Hardware
The term hardware covers all of those parts of a computer that are tangible objects. Circuits, displays, power supplies, cables, keyboards, printers and mice are all hardware.
History of computing hardware First Generation (Mechanical/Electromechanical) Calculators Antikythera mechanism, Difference Engine, Norden bombsight
Programmable Devices Jacquard loom, Analytical Engine, Harvard Mark I, Z3
Second Generation (Vacuum Tubes) Calculators Atanasoff-Berry Computer
Programmable Devices ENIAC, EDSAC, EDVAC, UNIVAC I
Third Generation (Discrete transistors and SSI, MSI, LSI Integrated circuits) Mainframes System/360, BUNCH
Minicomputer PDP-8, PDP-11, System/32, System/36
Fourth Generation (VLSI integrated circuits) Minicomputer VAX, AS/400
4-bit microcomputer Intel 4004, Intel 4040
8-bit microcomputer Intel 8008, Intel 8080, Motorola 6800, Motorola 6809, MOS Technology 6502, Zilog Z80
16-bit microcomputer 8088, Zilog Z8000, WDC 65816/65802
32-bit microcomputer 80386, Pentium, 68000, ARM architecture
64-bit microcomputer [14] x86-64, PowerPC, MIPS, SPARC
Embedded computer 8048, 8051
Personal computer Desktop computer, Home computer, Laptop computer, Personal digital assistant (PDA), Portable computer, Tablet computer, Wearable computer
Server class computer
Theoretical/experimental Quantum computer
Chemical computer
DNA computing
Optical computer
Other Hardware Topics Peripheral device (Input/output) Input Mouse, Keyboard, Joystick, Image scanner
Output Monitor, Printer
Both Floppy disk drive, Hard disk, Optical disc drive, Teleprinter
Computer busses Short range RS-232, SCSI, PCI, USB
Long range (Computer networking) Ethernet, ATM, FDDI
Software
Software refers to parts of the computer that have no material form; programs, data, protocols, etc are all software. When software is stored in hardware that cannot easily be modified (such as BIOS ROM in an IBM PC compatible), it is sometimes termed firmware to indicate that it falls into an area of uncertainty between hardware and software.
Computer software Operating system Unix/BSD UNIX System V, AIX, HP-UX, Solaris (SunOS), FreeBSD, NetBSD, IRIX
GNU/Linux List of Linux distributions, Comparison of Linux distributions
Microsoft Windows Windows 9x, Windows NT, Windows CE
DOS QDOS, PC-DOS, MS-DOS, FreeDOS
Mac OS Mac OS classic, Mac OS X
Embedded and real-time List of embedded operating systems
Experimental Amoeba, Oberon/Bluebottle, Plan 9 from Bell Labs
Library Multimedia DirectX, OpenGL, OpenAL
Programming library C standard library, Standard template library
Data Protocol TCP/IP, Kermit, FTP, HTTP, SMTP
File format HTML, XML, JPEG, MPEG, PNG
User interface Graphical user interface (WIMP) Microsoft Windows, GNOME, QNX Photon, CDE, GEM
Text user interface Command line interface, shells
Other
Application Office suite Word processing, Desktop publishing, Presentation program, Database management system, Scheduling & Time management, Spreadsheet, Accounting software
Internet Access Browser, E-mail client, Web server, Mail transfer agent, Instant messaging
Design and manufacturing Computer-aided design, Computer-aided manufacturing, Plant management, Robotic manufacturing, Supply chain management
Graphics Raster graphics editor, Vector graphics editor, 3D modeler, Animation editor, 3D computer graphics, Video editing, Image processing
Audio Digital audio editor, Audio playback, Mixing, Audio synthesis, Computer music
Software Engineering Compiler, Assembler, Interpreter, Debugger, Text Editor, Integrated development environment, Performance analysis, Revision control, Software configuration management
Educational Edutainment, Educational game, Serious game, Flight simulator
Games Strategy, Arcade, Puzzle, Simulation, First-person shooter, Platform, Massively multiplayer, Interactive fiction
Misc Artificial intelligence, Antivirus software, Malware scanner, Installer/Package management systems, File manager
Wednesday, February 20, 2008
Tuesday, February 19, 2008
Computer Glossary P - Z
P - S
palm A hand-held computer.
PC Personal computer. Generally refers to computers running Windows with a Pentium processor.
PC board Printed Circuit board. A board printed or etched with a circuit and processors. Power supplies, information storage devices, or changers are attached.
PDA Personal Digital Assistant. A hand-held computer that can store daily appointments, phone numbers, addresses, and other important information. Most PDAs link to a desktop or laptop computer to download or upload information.
PDF Portable Document Format. A format presented by Adobe Acrobat that allows documents to be shared over a variety of operating systems. Documents can contain words and pictures and be formatted to have electronic links to other parts of the document or to places on the web.
Pentium chip Intel's fifth generation of sophisticated high-speed microprocessors. Pentium means “the fifth element.”
peripheral Any external device attached to a computer to enhance operation. Examples include external hard drive, scanner, printer, speakers, keyboard, mouse, trackball, stylus and tablet, and joystick.
personal computer (PC) A single-user computer containing a central processing unit (CPU) and one or more memory circuits.
petabyte A measure of memory or storage capacity and is approximately a thousand terabytes.
petaflop A theoretical measure of a computer's speed and can be expressed as a thousand-trillion floating-point operations per second.
platform The operating system, such as UNIX®, Macintosh®, Windows®, on which a computer is based.
plug and play Computer hardware or peripherals that come set up with necessary software so that when attached to a computer, they are “recognized” by the computer and are ready to use.
pop-up menu A menu window that opens vertically or horizontally on-screen to display context-related options. Also called drop-down menu or pull-down menu.
Power PC A competitor of the Pentium chip. It is a new generation of powerful sophisticated microprocessors produced from an Apple-IBM-Motorola alliance.
printer A mechanical device for printing a computer's output on paper. There are three major types of printers: Dot matrix: creates individual letters, made up of a series of tiny ink dots, by punching a ribbon with the ends of tiny wires. (This type of printer is most often used in industrial settings, such as direct mail for labeling.) Ink jet: sprays tiny droplets of ink particles onto paper. Laser: uses a beam of light to reproduce the image of each page using a magnetic charge that attracts dry toner that is transferred to paper and sealed with heat.
program A precise series of instructions written in a computer language that tells the computer what to do and how to do it. Programs are also called “software” or “applications.”
programming language A series of instructions written by a programmer according to a given set of rules or conventions (“syntax”). High-level programming languages are independent of the device on which the application (or program) will eventually run; low-level languages are specific to each program or platform. Programming language instructions are converted into programs in language specific to a particular machine or operating system (“machine language”) so that the computer can interpret and carry out the instructions. Some common programming languages are BASIC, C, C++, dBASE, FORTRAN, and Perl.
puck An input device, like a mouse. It has a magnifying glass with crosshairs on the front of it that allows the operator to position it precisely when tracing a drawing for use with CAD-CAM software.
pull-down menu A menu window that opens vertically on-screen to display context-related options. Also called drop-down menu or pop-up menu.
push technology Internet tool that delivers specific information directly to a user's desktop, eliminating the need to surf for it. PointCast, which delivers news in user-defined categories, is a popular example of this technology.
QuickTime® Audio-visual software that allows movie-delivery via the Internet and e-mail. QuickTime mages are viewed on a monitor.
RAID Redundant Array of Inexpensive Disks. A method of spreading information across several disks set up to act as a unit, using two different techniques: Disk striping: storing a bit of information across several discs (instead of storing it all on one disc and hoping that the disc doesn't crash). Disk mirroring: simultaneously storing a copy of information on another disc so that the information can be recovered if the main disc crashes.
RAM Random Access Memory. One of two basic types of memory. Portions of programs are stored in RAM when the program is launched so that the program will run faster. Though a PC has a fixed amount of RAM, only portions of it will be accessed by the computer at any given time. Also called memory.
right-click Using the right mouse button to open context-sensitive drop-down menus.
ROM Read-Only Memory. One of two basic types of memory. ROM contains only permanent information put there by the manufacturer. Information in ROM cannot be altered, nor can the memory be dynamically allocated by the computer or its operator.
scanner An electronic device that uses light-sensing equipment to scan paper images such as text, photos, and illustrations and translate the images into signals that the computer can then store, modify, or distribute.
search engine Software that makes it possible to look for and retrieve material on the Internet, particularly the Web. Some popular search engines are Alta Vista, Google, HotBot, Yahoo!, Web Crawler, and Lycos.
server A computer that shares its resources and information with other computers, called clients, on a network.
shareware Software created by people who are willing to sell it at low cost or no cost for the gratification of sharing. It may be freestanding software, or it may add functionality to existing software.
software Computer programs; also called “applications.”
spider A process search engines use to investigate new pages on a web site and collect the information that needs to be put in their indices.
spreadsheet Software that allows one to calculate numbers in a format that is similar to pages in a conventional ledger.
storage Devices used to store massive amounts of information so that it can be readily retrieved. Devices include RAIDs, CD-ROMs, DVDs
streaming Taking packets of information (sound or visual) from the Internet and storing it in temporary files to allow it to play in continuous flow.
stylus and tablet A input device similar to a mouse. The stylus is pen shaped. It is used to “draw” on a tablet (like drawing on paper) and the tablet transfers the information to the computer. The tablet responds to pressure—the firmer the pressure used to draw, the thicker the line appears.
surfing Exploring the Internet.
surge protector A controller to protect the computer and make up for variances in voltage.
T – Z
telnet A way to communicate with a remote computer over a network.
trackball Input device that controls the position of the cursor on the screen; the unit is mounted near the keyboard, and movement is controlled by moving a ball.
terabytes (TB) A thousand gigabytes.
teraflop A measure of a computer's speed. It can be expressed as a trillion floating-point operations per second.
Trojan Horse See virus.
UNIX® A very powerful operating system used as the basis of many high-end computer applications.
upload The process of transferring information from a computer to a web site (or other remote location on a network). v. To transfer information from a computer to a web site (or other remote location on a network).
URL Uniform Resource Locator. 1. The protocol for identifying a document on the Web. 2. A Web address (e.g., www.census.gov). A URL is unique to each user. See also domain.
UPS Universal Power Supply or Uninterruptible Power Supply. An electrical power supply that includes a battery to provide enough power to a computer during an outage to back-up data and properly shut down.
USB Universal Serial Bus. An industry standard for connecting different compatible peripheral devices across multiple platforms. Devices include printers, digital cameras, scanners, game pads, joysticks, keyboards and mice, and storage devices. USB peripherals offer the use of plug-and-play convenience by eliminating the need to turn off or restart the computer when attaching a new peripheral. Users can connect USB peripherals whenever they need them. For example, a user producing a newsletter could easily swap a digital camera for a scanner-without any downtime. Small, simple, inexpensive, and easy to attach, USB supports simultaneous connection of up to 127 devices by attaching peripherals through interconnected external hubs.
USB hub A multiple-socket USB connecter that allows several USB-compatible devices to be connected to a computer.
USENET A large unmoderated and unedited bulletin board on the Internet that offers thousands of forums, called newsgroups. These range from newsgroups exchanging information on scientific advances to celebrity fan clubs.
user friendly A program or device whose use is intuitive to people with a nontechnical background.
video teleconferencing A remote “face-to-face chat,” when two or more people using a webcam and an Internet telephone connection chat online. The webcam enables both live voice and video.
virtual reality (VR) A technology that allows one to experience and interact with images in a simulated three-dimensional environment. For example, you could design a room in a house on your computer and actually feel that you are walking around in it even though it was never built. (The Holodeck in the science-fiction TV series Star Trek: Voyager would be the ultimate virtual reality.) Current technology requires the user to wear a special helmet, viewing goggles, gloves, and other equipment that transmits and receives information from the computer.
virus An unauthorized piece of computer code attached to a computer program or portions of a computer system that secretly copies itself from one computer to another by shared discs and over telephone and cable lines. It can destroy information stored on the computer, and in extreme cases, can destroy operability. Computers can be protected from viruses if the operator utilizes good virus prevention software and keeps the virus definitions up to date. Most viruses are not programmed to spread themselves. They have to be sent to another computer by e-mail, sharing, or applications. The worm is an exception, because it is programmed to replicate itself by sending copies to other computers listed in the e-mail address book in the computer. There are many kinds of viruses, for example: Boot viruses place some of their code in the start-up disk sector to automatically execute when booting. Therefore, when an infected machine boots, the virus loads and runs. File viruses attached to program files (files with the extension “.exe”). When you run the infected program, the virus code executes. Macro viruses copy their macros to templates and/or other application document files. Trojan Horse is a malicious, security-breaking program that is disguised as something benign such as a screen saver or game. Worm launches an application that destroys information on your hard drive. It also sends a copy of the virus to everyone in the computer's e-mail address book.
WAV A sound format (pronounced “wave”) used to reproduce sounds on a computer.
webcam A video camera/computer setup that takes live images and sends them to a Web browser.
Window A portion of a computer display used in a graphical interface that enables users to select commands by pointing to illustrations or symbols with a mouse. “Windows” is also the name Microsoft adopted for its popular operating system.
World Wide Web (“WWW” or “the Web”) A network of servers on the Internet that use hypertext-linked databases and files. It was developed in 1989 by Tim Berners-Lee, a British computer scientist, and is now the primary platform of the Internet. The feature that distinguishes the Web from other Internet applications is its ability to display graphics in addition to text.
word processor A computer system or program for setting, editing, revising, correcting, storing, and printing text.
Worm See virus.
WYSIWYG What You See Is What You Get. When using most word processors, page layout programs (See desktop publishing), and web page design programs, words and images will be displayed on the monitor as they will look on the printed page or web page.
palm A hand-held computer.
PC Personal computer. Generally refers to computers running Windows with a Pentium processor.
PC board Printed Circuit board. A board printed or etched with a circuit and processors. Power supplies, information storage devices, or changers are attached.
PDA Personal Digital Assistant. A hand-held computer that can store daily appointments, phone numbers, addresses, and other important information. Most PDAs link to a desktop or laptop computer to download or upload information.
PDF Portable Document Format. A format presented by Adobe Acrobat that allows documents to be shared over a variety of operating systems. Documents can contain words and pictures and be formatted to have electronic links to other parts of the document or to places on the web.
Pentium chip Intel's fifth generation of sophisticated high-speed microprocessors. Pentium means “the fifth element.”
peripheral Any external device attached to a computer to enhance operation. Examples include external hard drive, scanner, printer, speakers, keyboard, mouse, trackball, stylus and tablet, and joystick.
personal computer (PC) A single-user computer containing a central processing unit (CPU) and one or more memory circuits.
petabyte A measure of memory or storage capacity and is approximately a thousand terabytes.
petaflop A theoretical measure of a computer's speed and can be expressed as a thousand-trillion floating-point operations per second.
platform The operating system, such as UNIX®, Macintosh®, Windows®, on which a computer is based.
plug and play Computer hardware or peripherals that come set up with necessary software so that when attached to a computer, they are “recognized” by the computer and are ready to use.
pop-up menu A menu window that opens vertically or horizontally on-screen to display context-related options. Also called drop-down menu or pull-down menu.
Power PC A competitor of the Pentium chip. It is a new generation of powerful sophisticated microprocessors produced from an Apple-IBM-Motorola alliance.
printer A mechanical device for printing a computer's output on paper. There are three major types of printers: Dot matrix: creates individual letters, made up of a series of tiny ink dots, by punching a ribbon with the ends of tiny wires. (This type of printer is most often used in industrial settings, such as direct mail for labeling.) Ink jet: sprays tiny droplets of ink particles onto paper. Laser: uses a beam of light to reproduce the image of each page using a magnetic charge that attracts dry toner that is transferred to paper and sealed with heat.
program A precise series of instructions written in a computer language that tells the computer what to do and how to do it. Programs are also called “software” or “applications.”
programming language A series of instructions written by a programmer according to a given set of rules or conventions (“syntax”). High-level programming languages are independent of the device on which the application (or program) will eventually run; low-level languages are specific to each program or platform. Programming language instructions are converted into programs in language specific to a particular machine or operating system (“machine language”) so that the computer can interpret and carry out the instructions. Some common programming languages are BASIC, C, C++, dBASE, FORTRAN, and Perl.
puck An input device, like a mouse. It has a magnifying glass with crosshairs on the front of it that allows the operator to position it precisely when tracing a drawing for use with CAD-CAM software.
pull-down menu A menu window that opens vertically on-screen to display context-related options. Also called drop-down menu or pop-up menu.
push technology Internet tool that delivers specific information directly to a user's desktop, eliminating the need to surf for it. PointCast, which delivers news in user-defined categories, is a popular example of this technology.
QuickTime® Audio-visual software that allows movie-delivery via the Internet and e-mail. QuickTime mages are viewed on a monitor.
RAID Redundant Array of Inexpensive Disks. A method of spreading information across several disks set up to act as a unit, using two different techniques: Disk striping: storing a bit of information across several discs (instead of storing it all on one disc and hoping that the disc doesn't crash). Disk mirroring: simultaneously storing a copy of information on another disc so that the information can be recovered if the main disc crashes.
RAM Random Access Memory. One of two basic types of memory. Portions of programs are stored in RAM when the program is launched so that the program will run faster. Though a PC has a fixed amount of RAM, only portions of it will be accessed by the computer at any given time. Also called memory.
right-click Using the right mouse button to open context-sensitive drop-down menus.
ROM Read-Only Memory. One of two basic types of memory. ROM contains only permanent information put there by the manufacturer. Information in ROM cannot be altered, nor can the memory be dynamically allocated by the computer or its operator.
scanner An electronic device that uses light-sensing equipment to scan paper images such as text, photos, and illustrations and translate the images into signals that the computer can then store, modify, or distribute.
search engine Software that makes it possible to look for and retrieve material on the Internet, particularly the Web. Some popular search engines are Alta Vista, Google, HotBot, Yahoo!, Web Crawler, and Lycos.
server A computer that shares its resources and information with other computers, called clients, on a network.
shareware Software created by people who are willing to sell it at low cost or no cost for the gratification of sharing. It may be freestanding software, or it may add functionality to existing software.
software Computer programs; also called “applications.”
spider A process search engines use to investigate new pages on a web site and collect the information that needs to be put in their indices.
spreadsheet Software that allows one to calculate numbers in a format that is similar to pages in a conventional ledger.
storage Devices used to store massive amounts of information so that it can be readily retrieved. Devices include RAIDs, CD-ROMs, DVDs
streaming Taking packets of information (sound or visual) from the Internet and storing it in temporary files to allow it to play in continuous flow.
stylus and tablet A input device similar to a mouse. The stylus is pen shaped. It is used to “draw” on a tablet (like drawing on paper) and the tablet transfers the information to the computer. The tablet responds to pressure—the firmer the pressure used to draw, the thicker the line appears.
surfing Exploring the Internet.
surge protector A controller to protect the computer and make up for variances in voltage.
T – Z
telnet A way to communicate with a remote computer over a network.
trackball Input device that controls the position of the cursor on the screen; the unit is mounted near the keyboard, and movement is controlled by moving a ball.
terabytes (TB) A thousand gigabytes.
teraflop A measure of a computer's speed. It can be expressed as a trillion floating-point operations per second.
Trojan Horse See virus.
UNIX® A very powerful operating system used as the basis of many high-end computer applications.
upload The process of transferring information from a computer to a web site (or other remote location on a network). v. To transfer information from a computer to a web site (or other remote location on a network).
URL Uniform Resource Locator. 1. The protocol for identifying a document on the Web. 2. A Web address (e.g., www.census.gov). A URL is unique to each user. See also domain.
UPS Universal Power Supply or Uninterruptible Power Supply. An electrical power supply that includes a battery to provide enough power to a computer during an outage to back-up data and properly shut down.
USB Universal Serial Bus. An industry standard for connecting different compatible peripheral devices across multiple platforms. Devices include printers, digital cameras, scanners, game pads, joysticks, keyboards and mice, and storage devices. USB peripherals offer the use of plug-and-play convenience by eliminating the need to turn off or restart the computer when attaching a new peripheral. Users can connect USB peripherals whenever they need them. For example, a user producing a newsletter could easily swap a digital camera for a scanner-without any downtime. Small, simple, inexpensive, and easy to attach, USB supports simultaneous connection of up to 127 devices by attaching peripherals through interconnected external hubs.
USB hub A multiple-socket USB connecter that allows several USB-compatible devices to be connected to a computer.
USENET A large unmoderated and unedited bulletin board on the Internet that offers thousands of forums, called newsgroups. These range from newsgroups exchanging information on scientific advances to celebrity fan clubs.
user friendly A program or device whose use is intuitive to people with a nontechnical background.
video teleconferencing A remote “face-to-face chat,” when two or more people using a webcam and an Internet telephone connection chat online. The webcam enables both live voice and video.
virtual reality (VR) A technology that allows one to experience and interact with images in a simulated three-dimensional environment. For example, you could design a room in a house on your computer and actually feel that you are walking around in it even though it was never built. (The Holodeck in the science-fiction TV series Star Trek: Voyager would be the ultimate virtual reality.) Current technology requires the user to wear a special helmet, viewing goggles, gloves, and other equipment that transmits and receives information from the computer.
virus An unauthorized piece of computer code attached to a computer program or portions of a computer system that secretly copies itself from one computer to another by shared discs and over telephone and cable lines. It can destroy information stored on the computer, and in extreme cases, can destroy operability. Computers can be protected from viruses if the operator utilizes good virus prevention software and keeps the virus definitions up to date. Most viruses are not programmed to spread themselves. They have to be sent to another computer by e-mail, sharing, or applications. The worm is an exception, because it is programmed to replicate itself by sending copies to other computers listed in the e-mail address book in the computer. There are many kinds of viruses, for example: Boot viruses place some of their code in the start-up disk sector to automatically execute when booting. Therefore, when an infected machine boots, the virus loads and runs. File viruses attached to program files (files with the extension “.exe”). When you run the infected program, the virus code executes. Macro viruses copy their macros to templates and/or other application document files. Trojan Horse is a malicious, security-breaking program that is disguised as something benign such as a screen saver or game. Worm launches an application that destroys information on your hard drive. It also sends a copy of the virus to everyone in the computer's e-mail address book.
WAV A sound format (pronounced “wave”) used to reproduce sounds on a computer.
webcam A video camera/computer setup that takes live images and sends them to a Web browser.
Window A portion of a computer display used in a graphical interface that enables users to select commands by pointing to illustrations or symbols with a mouse. “Windows” is also the name Microsoft adopted for its popular operating system.
World Wide Web (“WWW” or “the Web”) A network of servers on the Internet that use hypertext-linked databases and files. It was developed in 1989 by Tim Berners-Lee, a British computer scientist, and is now the primary platform of the Internet. The feature that distinguishes the Web from other Internet applications is its ability to display graphics in addition to text.
word processor A computer system or program for setting, editing, revising, correcting, storing, and printing text.
Worm See virus.
WYSIWYG What You See Is What You Get. When using most word processors, page layout programs (See desktop publishing), and web page design programs, words and images will be displayed on the monitor as they will look on the printed page or web page.
Computer Glossary A - F
A - C
applet A small Java application that is downloaded by an ActiveX or Java-enabled web browser. Once it has been downloaded, the applet will run on the user's computer. Common applets include financial calculators and web drawing programs.
application Computer software that performs a task or set of tasks, such as word processing or drawing. Applications are also referred to as programs.
ASCII American Standard Code for Information Interchange, an encoding system for converting keyboard characters and instructions into the binary number code that the computer understands.
bandwidth The capacity of a networked connection. Bandwidth determines how much data can be sent along the networked wires. Bandwidth is particularly important for Internet connections, since greater bandwidth also means faster downloads.
binary code The most basic language a computer understands, it is composed of a series of 0s and 1s. The computer interprets the code to form numbers, letters, punctuation marks, and symbols.
bit (short for “binary digit”). The smallest piece of computer information, either the number 0 or 1.
boot
To start up a computer. Cold boot—restarting computer after having turned off the power. Warm boot—restarting computer without having turned off the power.
browser
Software used to navigate the Internet. Netscape Navigator and Microsoft Internet Explorer are today's most popular browsers for accessing the World Wide Web.
bug
A malfunction due to an error in the program or a defect in the equipment.
byte
Most computers use combinations of eight bits, called bytes, to represent one character of data or instructions. For example, the word “cat” has three characters, and it would be represented by three bytes.
cache
A small data-memory storage area that a computer can use to instantly re-access data instead of re-reading the data from the original source, such as a hard drive. Browsers use a cache to store web pages so that the user may view them again without reconnecting to the Web.
CAD-CAM
Computer Aided Drawing-Computer Aided Manufacturing. The instructions stored in a computer that will be translated to very precise operating instructions to a robot, such as for assembling cars or laser-cutting signage.
CD-ROM
Compact Disc Read-Only Memory. An optically read disc designed to hold information such as music, reference materials, or computer software. A single CD-ROM can hold around 640 megabytes of data, enough for several encyclopedias. Most software programs are now delivered on CD-ROMs.
CGI Common Gateway Interface. A programming standard that allows visitors to fill out form fields on a Web page and have that information interact with a database, possibly coming back to the user as another Web page.
CGI may also refer to Computer-Generated Imaging, the process in which sophisticated computer programs create still and animated graphics, such as special effects for movies.
chat
Typing text into a message box on a screen to engage in dialog with one or more people via the Internet or other network.
chip
A tiny wafer of silicon containing miniature electric circuits that can store millions of bits of information.
client
A single user of a network application that is operated from a server. A client/server architecture allows many people to use the same data simultaneously. The program's main component (the data) resides on a centralized server, with smaller components (user interface) on each client.
Cookie
A text file sent by a Web server that is stored on the hard drive of a computer and relays back to the Web server things about the user, his or her computer, and/or his or her computer activities.
CPU
Central Processing Unit. The brain of the computer.
cracker
A person who “breaks in” to a computer through a network, without authorization and with mischievous or destructive intent (a crime in some states).
crash
A hardware or software problem that causes information to be lost or the computer to malfunction. Sometimes a crash can cause permanent damage to a computer.
cursor
A moving position-indicator displayed on a computer monitor that shows a computer operator where the next action or operation will take place.
cyberspace Slang for the Internet.
D - F
database
A collection of similar information stored in a file, such as a database of addresses. This information may be created and stored in a database management system (DBMS).
debug
Slang. To find and correct equipment defects or program malfunctions.
default
The pre-defined configuration of a system or an application. In most programs, the defaults can be changed to reflect personal preferences.
desktop
The main directory of the user interface. Desktops usually contain icons that represent links to the hard drive, a network (if there is one), and a trash or recycling can for files to be deleted. It can also display icons of frequently used applications, as requested by the user.
desktop publishing
The production of publication-quality documents using a personal computer in combination with text, graphics, and page layout programs.
directory
A list of files stored in the computer.
disk Two distinct types. The names refer to the media inside the container: A hard disc stores vast amounts of data. It is usually inside the computer but can be a separate peripheral on the outside. Hard discs are made up of several rigid coated metal discs. Currently, hard discs can store 15 to 30 Gb (gigabytes) A floppy disc, 3.5" square, usually inserted into the computer and can store about 1.4 megabytes of data. The 3.5" square “floppies” have a very thin, flexible disc inside. There is also an intermediate-sized floppy disc, trademarked Zip discs, which can store 250 megabytes of data.
disk drive
The equipment that operates a hard or floppy disc.
documentation
The instruction manual for a piece of hardware or software.
domain
Represents an IP (Internet Protocol) address or set of IP addresses that comprise a domain. The domain name appears in URLs to identify web pages or in email addresses. For example, the email address for the First Lady is first.lady@whitehouse.gov, “whitehouse.gov” being the domain name. Each domain name ends with a suffix that indicates what “top level domain” it belongs to. These are: “.com” for commercial, “.gov” for government, “.org” for organization, “.edu” for educational institution, “.biz” for business, “.info” for information, “.tv” for television, “.ws” for website. Domain suffixes may also indicate the country in which the domain is registered. No two parties can ever hold the same domain name.
domain name
The name of a network or computer linked to the Internet. Domains are defined by a common IP address or set of similar IP (Internet Protocol) addresses.
download The process of transferring information from a web site (or other remote location on a network) to the computer. It is possible to “download a file” or “view a download.”
v. To transfer information from a web site (or other remote location on a network) to the computer.
DOS
Disk Operating System. An operating system designed for early IBM-compatible PCs.
Drop-down menu
A menu window that opens vertically on-screen to display context-related options. Also called pop-up menu or pull-down menu.
DSL
Digital Subscriber Line. A method of connecting to the Internet via a phone line. A DSL connection uses copper telephone lines but is able to relay data at much higher speeds than modems and does not interfere with telephone use.
DVD
Digital Video Disc—Similar to a CD-ROM, it stores and plays both audio and video.
ebook
An electronic (usually hand-held) reading device that allows a person to view digitally stored reading materials.
email
Electronic mail; messages, including memos or letters, sent electronically between networked computers that may be across the office or around the world.
emoticon
A text-based expression of emotion created from ASCII characters that mimics a facial expression when viewed with your head tilted to the left. Here are some examples:
:-) Smiling
:-( Frowning
;-) Winking
:_( Crying
encryption
The process of transmitting scrambled data so that only authorized recipients can unscramble it. For instance, encryption is used to scramble credit card information when purchases are made over the Internet.
ethernet
A type of network.
ethernet card
A board inside a computer to which a network cable can be attached.
file
A set of data that is stored in the computer.
firewall
A set of security programs that protect a computer from outside interference or access via the Internet.
Firewire
Apple® Computer's high-speed data transfer. Frequently used to import video to a computer.
folder
A structure for containing electronic files. In some operating systems, it is called a “directory.”
fonts
Sets of typefaces (or characters) that come in different styles and sizes.
freeware
Software created by people who are willing to give it away for the satisfaction of sharing or knowing they helped to simplify other people's lives. It may be freestanding software, or it may add functionality to existing software.
FTP File Transfer Protocol. A format and set of rules for transferring files from a host to a remote computer.
applet A small Java application that is downloaded by an ActiveX or Java-enabled web browser. Once it has been downloaded, the applet will run on the user's computer. Common applets include financial calculators and web drawing programs.
application Computer software that performs a task or set of tasks, such as word processing or drawing. Applications are also referred to as programs.
ASCII American Standard Code for Information Interchange, an encoding system for converting keyboard characters and instructions into the binary number code that the computer understands.
bandwidth The capacity of a networked connection. Bandwidth determines how much data can be sent along the networked wires. Bandwidth is particularly important for Internet connections, since greater bandwidth also means faster downloads.
binary code The most basic language a computer understands, it is composed of a series of 0s and 1s. The computer interprets the code to form numbers, letters, punctuation marks, and symbols.
bit (short for “binary digit”). The smallest piece of computer information, either the number 0 or 1.
boot
To start up a computer. Cold boot—restarting computer after having turned off the power. Warm boot—restarting computer without having turned off the power.
browser
Software used to navigate the Internet. Netscape Navigator and Microsoft Internet Explorer are today's most popular browsers for accessing the World Wide Web.
bug
A malfunction due to an error in the program or a defect in the equipment.
byte
Most computers use combinations of eight bits, called bytes, to represent one character of data or instructions. For example, the word “cat” has three characters, and it would be represented by three bytes.
cache
A small data-memory storage area that a computer can use to instantly re-access data instead of re-reading the data from the original source, such as a hard drive. Browsers use a cache to store web pages so that the user may view them again without reconnecting to the Web.
CAD-CAM
Computer Aided Drawing-Computer Aided Manufacturing. The instructions stored in a computer that will be translated to very precise operating instructions to a robot, such as for assembling cars or laser-cutting signage.
CD-ROM
Compact Disc Read-Only Memory. An optically read disc designed to hold information such as music, reference materials, or computer software. A single CD-ROM can hold around 640 megabytes of data, enough for several encyclopedias. Most software programs are now delivered on CD-ROMs.
CGI Common Gateway Interface. A programming standard that allows visitors to fill out form fields on a Web page and have that information interact with a database, possibly coming back to the user as another Web page.
CGI may also refer to Computer-Generated Imaging, the process in which sophisticated computer programs create still and animated graphics, such as special effects for movies.
chat
Typing text into a message box on a screen to engage in dialog with one or more people via the Internet or other network.
chip
A tiny wafer of silicon containing miniature electric circuits that can store millions of bits of information.
client
A single user of a network application that is operated from a server. A client/server architecture allows many people to use the same data simultaneously. The program's main component (the data) resides on a centralized server, with smaller components (user interface) on each client.
Cookie
A text file sent by a Web server that is stored on the hard drive of a computer and relays back to the Web server things about the user, his or her computer, and/or his or her computer activities.
CPU
Central Processing Unit. The brain of the computer.
cracker
A person who “breaks in” to a computer through a network, without authorization and with mischievous or destructive intent (a crime in some states).
crash
A hardware or software problem that causes information to be lost or the computer to malfunction. Sometimes a crash can cause permanent damage to a computer.
cursor
A moving position-indicator displayed on a computer monitor that shows a computer operator where the next action or operation will take place.
cyberspace Slang for the Internet.
D - F
database
A collection of similar information stored in a file, such as a database of addresses. This information may be created and stored in a database management system (DBMS).
debug
Slang. To find and correct equipment defects or program malfunctions.
default
The pre-defined configuration of a system or an application. In most programs, the defaults can be changed to reflect personal preferences.
desktop
The main directory of the user interface. Desktops usually contain icons that represent links to the hard drive, a network (if there is one), and a trash or recycling can for files to be deleted. It can also display icons of frequently used applications, as requested by the user.
desktop publishing
The production of publication-quality documents using a personal computer in combination with text, graphics, and page layout programs.
directory
A list of files stored in the computer.
disk Two distinct types. The names refer to the media inside the container: A hard disc stores vast amounts of data. It is usually inside the computer but can be a separate peripheral on the outside. Hard discs are made up of several rigid coated metal discs. Currently, hard discs can store 15 to 30 Gb (gigabytes) A floppy disc, 3.5" square, usually inserted into the computer and can store about 1.4 megabytes of data. The 3.5" square “floppies” have a very thin, flexible disc inside. There is also an intermediate-sized floppy disc, trademarked Zip discs, which can store 250 megabytes of data.
disk drive
The equipment that operates a hard or floppy disc.
documentation
The instruction manual for a piece of hardware or software.
domain
Represents an IP (Internet Protocol) address or set of IP addresses that comprise a domain. The domain name appears in URLs to identify web pages or in email addresses. For example, the email address for the First Lady is first.lady@whitehouse.gov, “whitehouse.gov” being the domain name. Each domain name ends with a suffix that indicates what “top level domain” it belongs to. These are: “.com” for commercial, “.gov” for government, “.org” for organization, “.edu” for educational institution, “.biz” for business, “.info” for information, “.tv” for television, “.ws” for website. Domain suffixes may also indicate the country in which the domain is registered. No two parties can ever hold the same domain name.
domain name
The name of a network or computer linked to the Internet. Domains are defined by a common IP address or set of similar IP (Internet Protocol) addresses.
download The process of transferring information from a web site (or other remote location on a network) to the computer. It is possible to “download a file” or “view a download.”
v. To transfer information from a web site (or other remote location on a network) to the computer.
DOS
Disk Operating System. An operating system designed for early IBM-compatible PCs.
Drop-down menu
A menu window that opens vertically on-screen to display context-related options. Also called pop-up menu or pull-down menu.
DSL
Digital Subscriber Line. A method of connecting to the Internet via a phone line. A DSL connection uses copper telephone lines but is able to relay data at much higher speeds than modems and does not interfere with telephone use.
DVD
Digital Video Disc—Similar to a CD-ROM, it stores and plays both audio and video.
ebook
An electronic (usually hand-held) reading device that allows a person to view digitally stored reading materials.
Electronic mail; messages, including memos or letters, sent electronically between networked computers that may be across the office or around the world.
emoticon
A text-based expression of emotion created from ASCII characters that mimics a facial expression when viewed with your head tilted to the left. Here are some examples:
:-) Smiling
:-( Frowning
;-) Winking
:_( Crying
encryption
The process of transmitting scrambled data so that only authorized recipients can unscramble it. For instance, encryption is used to scramble credit card information when purchases are made over the Internet.
ethernet
A type of network.
ethernet card
A board inside a computer to which a network cable can be attached.
file
A set of data that is stored in the computer.
firewall
A set of security programs that protect a computer from outside interference or access via the Internet.
Firewire
Apple® Computer's high-speed data transfer. Frequently used to import video to a computer.
folder
A structure for containing electronic files. In some operating systems, it is called a “directory.”
fonts
Sets of typefaces (or characters) that come in different styles and sizes.
freeware
Software created by people who are willing to give it away for the satisfaction of sharing or knowing they helped to simplify other people's lives. It may be freestanding software, or it may add functionality to existing software.
FTP File Transfer Protocol. A format and set of rules for transferring files from a host to a remote computer.
Monday, February 18, 2008
Computer Production Market
The market for computer products is a multi-billion dollar business where one can find a perfect balance of technology and efficiency. The huge industrial market is lead by such names as IBM, Hewlett Packard, and Compaq. In the world today, computers are used for a variety of tasks and play a crucial role in the areas of academics and business. The steps that are taken to bring the computer from several small components to a desktop product are organization of the manufacturing facility, assembly of hardware, installation of software, and a test process. The production of a high quality product is important to computer buyers. The following discussion demonstrates steps large corporations take to make an efficient computer. Companies such as IBM and Apple computers are well known in the computer industry. These companies have several manufacturing facilities around the world where thousands of computers are built. Manufacturing factories, which typically range between “75,000 to 200,000 square feet”() in size, produce approximately 14,000 systems weekly. Companies generally use 2 methods of computer assembly. One method involves complete unit assembly by one person, the other being group assembly where several people construct a single computer (the latter method is known as assembly line production). A factory employing the single unit assembly method produces about 40 to 60 computers a day (this number varies base on the complexity of the system being assembled). The assembly line method yields approximately 70 computers a day in the average factory. The assembly line method is the most efficient way to produce computes as individual workers become highly specialized in a specific task. In addition, the next person down the ‘line’ can check the pervious person’s work to check for errors. “Additional inspection [, as used on assembly lines] tends to increase the computer’s quality”(). The first step in manufacturing a computer is for the designer to consider a balance between economic need (customers price level) with computer power and practicality. Manufacturers try to make the best computer (in a given price range) for the lowest cost. Once a specific model is designed the company orders the high quality parts from their own component manufacturing divisions or outside suppliers. Inventory control is an important part of acquiring components as, to remain efficient, the company tries to avoid overstocking. Manufacturers take note of the consumer demand, on a daily basis to efficiently establish quantities for the production line. Top manufactures such as IBM and Apple buy computer components for their products based on “availability, quality and priority of the configuration” (). When assembling a computer, there are 8 to 10 major components installed including the processor speed chip, the motherboard, RAM (Random Access Memory), diskette drive, modem or network card, video card, hard drive, sound card, and CD-ROM. Before the components are placed into the computer, each part undergoes an extensive testing process called “quality control” (). Quality control ensures that faulty systems are not shipped. As an initial step, prior to the assembly process, an inspection of the outer case to ensure that there are no scratches or defects. The brand name and indicator labels are put onto the computer case at this time. Next the motherboard is installed and prepared for the processor chip. The chip (which is often a Pentium chip) is attached to the motherboard along with the RAM component. Once the chip and RAM are installed, the internal speakers and sound card are placed into the case. The hard drive, disk drive and CD-ROM drive are in snuggly attached to the computer chassis. All these components are then attached to the motherboard with cables so that they may communicate with each other. Power supply is then applied to the computer and other additional components such as the video card, and modem are added near a final stage of assembly. After all these components are installed to create the finished ‘PC’, the unit is thoroughly inspected to ensures that all the cables connections are in place and all other defects are fixed. Inspectors also ensure that cables are in appropriate places so that they do not touch components. This is important as heat given off components, while operating can cause minor explosions. The CMOS (complementary metal-oxide semiconductor- circuitry for the memory and processor) is set up at this time. The top cover is placed onto the computer and it is shipped off for further testing. All companies differ in their testing of finished products. A common in most companies includes the 48-hour burn in period. This period is very similar to the burn in period that a car undergoes following production. After the 48-hour burn in, final diagnostic tests are completed to ensure all components are working well. If a computer is ordered with sound cards, speakers are attached to the unit and they also are tested. Mouse and keyboard components are tested manually by connecting a testing mouse and keyboard to the ports. The computer is then shipped from the manufacturing site to the distribution center. At the center, additional tests are possible as computers are randomly checked and inspected. The computer is then further shipped to department or retail stores for sale to the consumer. In conclusion, the production of a computer from a number of components to a finished product is a complex procedure. It is crucial to have a well-organized computer manufacturing facility, and it is important that assembly and insulation of all components is carried out accurately. Final testing is the concluding step in computer manufacturing process. The testing phase is most important, as consumers demand high quality and efficient products. In society today, computers are essential for the flow of information and important technical tasks. The usefulness of the computer and subsequent consumer demand for improved models will keep pressure on manufactures to build more efficient, high quality machines in future years.
Computer Production Market
The market for computer products is a multi-billion dollar business where one can find a perfect balance of technology and efficiency. The huge industrial market is lead by such names as IBM, Hewlett Packard, and Compaq. In the world today, computers are used for a variety of tasks and play a crucial role in the areas of academics and business. The steps that are taken to bring the computer from several small components to a desktop product are organization of the manufacturing facility, assembly of hardware, installation of software, and a test process. The production of a high quality product is important to computer buyers. The following discussion demonstrates steps large corporations take to make an efficient computer. Companies such as IBM and Apple computers are well known in the computer industry. These companies have several manufacturing facilities around the world where thousands of computers are built. Manufacturing factories, which typically range between “75,000 to 200,000 square feet”() in size, produce approximately 14,000 systems weekly. Companies generally use 2 methods of computer assembly. One method involves complete unit assembly by one person, the other being group assembly where several people construct a single computer (the latter method is known as assembly line production). A factory employing the single unit assembly method produces about 40 to 60 computers a day (this number varies base on the complexity of the system being assembled). The assembly line method yields approximately 70 computers a day in the average factory. The assembly line method is the most efficient way to produce computes as individual workers become highly specialized in a specific task. In addition, the next person down the ‘line’ can check the pervious person’s work to check for errors. “Additional inspection [, as used on assembly lines] tends to increase the computer’s quality”(). The first step in manufacturing a computer is for the designer to consider a balance between economic need (customers price level) with computer power and practicality. Manufacturers try to make the best computer (in a given price range) for the lowest cost. Once a specific model is designed the company orders the high quality parts from their own component manufacturing divisions or outside suppliers. Inventory control is an important part of acquiring components as, to remain efficient, the company tries to avoid overstocking. Manufacturers take note of the consumer demand, on a daily basis to efficiently establish quantities for the production line. Top manufactures such as IBM and Apple buy computer components for their products based on “availability, quality and priority of the configuration” (). When assembling a computer, there are 8 to 10 major components installed including the processor speed chip, the motherboard, RAM (Random Access Memory), diskette drive, modem or network card, video card, hard drive, sound card, and CD-ROM. Before the components are placed into the computer, each part undergoes an extensive testing process called “quality control” (). Quality control ensures that faulty systems are not shipped. As an initial step, prior to the assembly process, an inspection of the outer case to ensure that there are no scratches or defects. The brand name and indicator labels are put onto the computer case at this time. Next the motherboard is installed and prepared for the processor chip. The chip (which is often a Pentium chip) is attached to the motherboard along with the RAM component. Once the chip and RAM are installed, the internal speakers and sound card are placed into the case. The hard drive, disk drive and CD-ROM drive are in snuggly attached to the computer chassis. All these components are then attached to the motherboard with cables so that they may communicate with each other. Power supply is then applied to the computer and other additional components such as the video card, and modem are added near a final stage of assembly. After all these components are installed to create the finished ‘PC’, the unit is thoroughly inspected to ensures that all the cables connections are in place and all other defects are fixed. Inspectors also ensure that cables are in appropriate places so that they do not touch components. This is important as heat given off components, while operating can cause minor explosions. The CMOS (complementary metal-oxide semiconductor- circuitry for the memory and processor) is set up at this time. The top cover is placed onto the computer and it is shipped off for further testing. All companies differ in their testing of finished products. A common in most companies includes the 48-hour burn in period. This period is very similar to the burn in period that a car undergoes following production. After the 48-hour burn in, final diagnostic tests are completed to ensure all components are working well. If a computer is ordered with sound cards, speakers are attached to the unit and they also are tested. Mouse and keyboard components are tested manually by connecting a testing mouse and keyboard to the ports. The computer is then shipped from the manufacturing site to the distribution center. At the center, additional tests are possible as computers are randomly checked and inspected. The computer is then further shipped to department or retail stores for sale to the consumer. In conclusion, the production of a computer from a number of components to a finished product is a complex procedure. It is crucial to have a well-organized computer manufacturing facility, and it is important that assembly and insulation of all components is carried out accurately. Final testing is the concluding step in computer manufacturing process. The testing phase is most important, as consumers demand high quality and efficient products. In society today, computers are essential for the flow of information and important technical tasks. The usefulness of the computer and subsequent consumer demand for improved models will keep pressure on manufactures to build more efficient, high quality machines in future years.
Saturday, February 16, 2008
All About Computer Viruses
Your computer is as slow as molasses. Your mouse freezes every 15 minutes, and that Microsoft Word program just won’t seem to open.
You might have a virus.
Just what exactly is a virus? What kind is in your computer? How did it get there? How is it spreading and wreaking such havoc? And why is it bothering with your computer anyway?
Viruses are pieces of programming code that make copies of themselves, or replicate, inside your computer without asking your explicit written permission to do so. Forget getting your permission down on paper. Viruses don’t bother to seek your permission at all! Very invasive.
In comparison, there are pieces of code that might replicate inside your computer, say something your IT guy thinks you need. But the code spreads, perhaps throughout your office network, with your consent (or at least your IT guy’s consent). These types of replicating code are called agents, said Jimmy Kuo, a research fellow with McAfee AVERT, a research arm of anti-virus software-maker McAfee Inc.
In this article, though, we’re not talking about the good guys, or the agents. We’ll be talking about the bad guys, the viruses.
A long, long time ago in computer years, like five, most viruses were comprised of a similar breed. They entered your computer perhaps through an email attachment or a floppy disk (remember those?). Then they attached themselves to one of your files, say your Microsoft Word program.
When you opened your Microsoft Word program, the virus replicated and attached itself to other files. These could be other random files on your hard drive, the files furthest away from your Microsoft Word program, or other files, depending on how the virus writer wanted the virus to behave.
This virus code could contain hundreds or thousands of instructions. When it replicates it inserts those instructions, into the files it infects, said Carey Nachenberg, Chief Architect at Symantec Research Labs, an arm of anti-virus software-maker Symantec. Corp.
Because so many other types of viruses exist now, the kind just described is called a classic virus. Classic viruses still exist but they’re not quite as prevalent as they used to be. (Perhaps we could put classic viruses on the shelf with Hemingway and Dickens.)
These days, in the modern era, viruses are known to spread through vulnerabilities in web browsers, files shared over the internet, emails themselves, and computer networks.
As far as web browsers are concerned, Microsoft’s Internet Explorer takes most of the heat for spreading viruses because it’s used by more people for web surfing than any other browser.
Nevertheless, “Any web browser potentially has vulnerabilities,” Nachenberg said.
For instance, let’s say you go to a website in IE you have every reason to think is safe, Nachenberg said.
But unfortunately it isn’t. It has virus code hidden in its background that IE isn’t protecting you from. While you’re looking at the site, the virus is downloaded onto your computer, he said. That’s one way of catching a nasty virus.
During the past two years, another prevalent way to catch a virus has been through downloads computer users share with one another, mostly on music sharing sites, Kuo said. On Limewire or Kazaa, for instance, teenagers or other music enthusiasts might think they’re downloading that latest Justin Timberlake song, when in reality they’re downloading a virus straight into their computer. It’s easy for a virus writer to put a download with a virus on one of these sites because everyone’s sharing with everyone else anyway.
Here’s one you might not have thought of. If you use Outlook or Outlook Express to send and receive email, do you have a preview pane below your list of emails that shows the contents of the email you have highlighted? If so, you may be putting yourself at risk.
Some viruses, though a small percentage according to Nachenberg, are inserted straight into emails themselves.
Forget opening the attachment. All you have to do is view the email to potentially get a virus, Kuo added. For instance, have you ever opened or viewed an email that states it’s “loading”? Well, once everything is “loaded,” a virus in the email might just load onto your computer.
So if I were you, I’d click on View on the toolbar in your Outlook or Outlook Express and close the preview pane. (You have to click on View and then Layout in Outlook Express.)
On a network at work? You could get a virus that way. Worms are viruses that come into your computer via networks, Kuo said. They travel from machine to machine and, unlike, the classic viruses, they attack the machine itself rather than individual files.
Worms sit in your working memory, or RAM, Nachenberg said.
OK, so we’ve talked about how the viruses get into a computer. How do they cause so much damage once they’re there?
Let’s say you’ve caught a classic virus, one that replicates and attacks various files on your computer. Let’s go back to the example of the virus that initially infects your Microsoft Word program.
Well, it might eventually cause that program to crash, Nachenberg said. It also might cause damage to your computer as it looks for new targets to infect.
This process of infecting targets and looking for new ones could eventually use up your computer’s ability to function, he said.
Often the destruction a virus causes is pegged to a certain event or date and time, called a trigger. For instance, a virus could be programmed to lay dormant until January 28. When that date rolls around, though, it may be programmed to do something as innocuous but annoying as splash popups on your screen, or something as severe as reformat your computer’s hard drive, Nachenberg said.
There are other potential reasons, though, for a virus to cause your computer to be acting slow or in weird ways. And that leads us to a new segment – the reason virus writers would want to waste their time creating viruses in the first place.
The majority of viruses are still written by teenagers looking for some notoriety, Nachenberg said. But a growing segment of the virus-writing population has other intentions in mind.
For these other intentions, we first need to explain the “backdoor” concept.
The sole purpose of some viruses is to create a vulnerability in your computer. Once it creates this hole of sorts, or backdoor, it signals home to mama or dada virus writer (kind of like in E.T.). Once the virus writer receives the signal, they can use and abuse your computer to their own likings.
Trojans are sometimes used to open backdoors. In fact that is usually their sole purpose, Kuo said.
Trojans are pieces of code you might download onto your computer, say, from a newsgroup. As in the Trojan War they are named after, they are usually disguised as innocuous pieces of code. But Trojans aren’t considered viruses because they don’t replicate.
Now back to the real viruses. Let’s say we have Joe Shmo virus writer. He sends out a virus that ends up infecting a thousand machines. But he doesn’t want the feds on his case. So he instructs the viruses on the various machines to send their signals, not of course to his computer, but to a place that can’t be traced. Hotmail email happens to be an example of one such place, Kuo said.
OK, so the virus writers now control these computers. What will they use them for?
One use is to send spam. Once that backdoor is open, they bounce spam off of those computers and send it to other machines, Nachenberg said.
That’s right. Some spam you have in your email right now may have been originally sent to other innocent computers before it came to yours so that it could remain in disguise. If the authorities could track down the original senders of spam, they could crack down on spam itself. Spam senders don’t want that.
Ever heard of phishing emails? Those are the ones that purport to be from your internet service provider or bank. They typically request some information from you, like your credit card number. The problem is, they’re NOT from your internet service provider or your bank. They’re from evil people after your credit card number! Well, these emails are often sent the same way spam is sent, by sending them via innocent computers.
Of course makers of anti-virus software use a variety of methods to combat the onslaught of viruses. Norton, for instance, uses signature scanning, Nachenberg said.
Signature scanning is similar to the process of looking for DNA fingerprints, he said. Norton examines programming code to find what viruses are made of. It adds those bad instructions it finds to its large database of other bad code. Then it uses this vast database to seek out and match the code in it with similar code in your computer. When it finds such virus code, it lets you know!
You might have a virus.
Just what exactly is a virus? What kind is in your computer? How did it get there? How is it spreading and wreaking such havoc? And why is it bothering with your computer anyway?
Viruses are pieces of programming code that make copies of themselves, or replicate, inside your computer without asking your explicit written permission to do so. Forget getting your permission down on paper. Viruses don’t bother to seek your permission at all! Very invasive.
In comparison, there are pieces of code that might replicate inside your computer, say something your IT guy thinks you need. But the code spreads, perhaps throughout your office network, with your consent (or at least your IT guy’s consent). These types of replicating code are called agents, said Jimmy Kuo, a research fellow with McAfee AVERT, a research arm of anti-virus software-maker McAfee Inc.
In this article, though, we’re not talking about the good guys, or the agents. We’ll be talking about the bad guys, the viruses.
A long, long time ago in computer years, like five, most viruses were comprised of a similar breed. They entered your computer perhaps through an email attachment or a floppy disk (remember those?). Then they attached themselves to one of your files, say your Microsoft Word program.
When you opened your Microsoft Word program, the virus replicated and attached itself to other files. These could be other random files on your hard drive, the files furthest away from your Microsoft Word program, or other files, depending on how the virus writer wanted the virus to behave.
This virus code could contain hundreds or thousands of instructions. When it replicates it inserts those instructions, into the files it infects, said Carey Nachenberg, Chief Architect at Symantec Research Labs, an arm of anti-virus software-maker Symantec. Corp.
Because so many other types of viruses exist now, the kind just described is called a classic virus. Classic viruses still exist but they’re not quite as prevalent as they used to be. (Perhaps we could put classic viruses on the shelf with Hemingway and Dickens.)
These days, in the modern era, viruses are known to spread through vulnerabilities in web browsers, files shared over the internet, emails themselves, and computer networks.
As far as web browsers are concerned, Microsoft’s Internet Explorer takes most of the heat for spreading viruses because it’s used by more people for web surfing than any other browser.
Nevertheless, “Any web browser potentially has vulnerabilities,” Nachenberg said.
For instance, let’s say you go to a website in IE you have every reason to think is safe, Nachenberg said.
But unfortunately it isn’t. It has virus code hidden in its background that IE isn’t protecting you from. While you’re looking at the site, the virus is downloaded onto your computer, he said. That’s one way of catching a nasty virus.
During the past two years, another prevalent way to catch a virus has been through downloads computer users share with one another, mostly on music sharing sites, Kuo said. On Limewire or Kazaa, for instance, teenagers or other music enthusiasts might think they’re downloading that latest Justin Timberlake song, when in reality they’re downloading a virus straight into their computer. It’s easy for a virus writer to put a download with a virus on one of these sites because everyone’s sharing with everyone else anyway.
Here’s one you might not have thought of. If you use Outlook or Outlook Express to send and receive email, do you have a preview pane below your list of emails that shows the contents of the email you have highlighted? If so, you may be putting yourself at risk.
Some viruses, though a small percentage according to Nachenberg, are inserted straight into emails themselves.
Forget opening the attachment. All you have to do is view the email to potentially get a virus, Kuo added. For instance, have you ever opened or viewed an email that states it’s “loading”? Well, once everything is “loaded,” a virus in the email might just load onto your computer.
So if I were you, I’d click on View on the toolbar in your Outlook or Outlook Express and close the preview pane. (You have to click on View and then Layout in Outlook Express.)
On a network at work? You could get a virus that way. Worms are viruses that come into your computer via networks, Kuo said. They travel from machine to machine and, unlike, the classic viruses, they attack the machine itself rather than individual files.
Worms sit in your working memory, or RAM, Nachenberg said.
OK, so we’ve talked about how the viruses get into a computer. How do they cause so much damage once they’re there?
Let’s say you’ve caught a classic virus, one that replicates and attacks various files on your computer. Let’s go back to the example of the virus that initially infects your Microsoft Word program.
Well, it might eventually cause that program to crash, Nachenberg said. It also might cause damage to your computer as it looks for new targets to infect.
This process of infecting targets and looking for new ones could eventually use up your computer’s ability to function, he said.
Often the destruction a virus causes is pegged to a certain event or date and time, called a trigger. For instance, a virus could be programmed to lay dormant until January 28. When that date rolls around, though, it may be programmed to do something as innocuous but annoying as splash popups on your screen, or something as severe as reformat your computer’s hard drive, Nachenberg said.
There are other potential reasons, though, for a virus to cause your computer to be acting slow or in weird ways. And that leads us to a new segment – the reason virus writers would want to waste their time creating viruses in the first place.
The majority of viruses are still written by teenagers looking for some notoriety, Nachenberg said. But a growing segment of the virus-writing population has other intentions in mind.
For these other intentions, we first need to explain the “backdoor” concept.
The sole purpose of some viruses is to create a vulnerability in your computer. Once it creates this hole of sorts, or backdoor, it signals home to mama or dada virus writer (kind of like in E.T.). Once the virus writer receives the signal, they can use and abuse your computer to their own likings.
Trojans are sometimes used to open backdoors. In fact that is usually their sole purpose, Kuo said.
Trojans are pieces of code you might download onto your computer, say, from a newsgroup. As in the Trojan War they are named after, they are usually disguised as innocuous pieces of code. But Trojans aren’t considered viruses because they don’t replicate.
Now back to the real viruses. Let’s say we have Joe Shmo virus writer. He sends out a virus that ends up infecting a thousand machines. But he doesn’t want the feds on his case. So he instructs the viruses on the various machines to send their signals, not of course to his computer, but to a place that can’t be traced. Hotmail email happens to be an example of one such place, Kuo said.
OK, so the virus writers now control these computers. What will they use them for?
One use is to send spam. Once that backdoor is open, they bounce spam off of those computers and send it to other machines, Nachenberg said.
That’s right. Some spam you have in your email right now may have been originally sent to other innocent computers before it came to yours so that it could remain in disguise. If the authorities could track down the original senders of spam, they could crack down on spam itself. Spam senders don’t want that.
Ever heard of phishing emails? Those are the ones that purport to be from your internet service provider or bank. They typically request some information from you, like your credit card number. The problem is, they’re NOT from your internet service provider or your bank. They’re from evil people after your credit card number! Well, these emails are often sent the same way spam is sent, by sending them via innocent computers.
Of course makers of anti-virus software use a variety of methods to combat the onslaught of viruses. Norton, for instance, uses signature scanning, Nachenberg said.
Signature scanning is similar to the process of looking for DNA fingerprints, he said. Norton examines programming code to find what viruses are made of. It adds those bad instructions it finds to its large database of other bad code. Then it uses this vast database to seek out and match the code in it with similar code in your computer. When it finds such virus code, it lets you know!
Thursday, February 14, 2008
Early Computers: A History of Computing
Computers are a part of our everyday lives, but about two decades ago, computers were just beginning to enter homes. Many people don’t realize what the computer evolved from, and the speed at which computer technology has taken to arrive to what it is today.
The earliest know computer is the abacus, invented by the Chinese in 2600 B.C. Not many people consider this to be a computer, but by definition, it is. One of the more recent early computers was built by Herman Hollerith, who invented a machine that used a system of cards with holes in them. By using these cards he was able to calculate the United State Census. Hollerith’s Computer Tabulating-Recording Company changed its name in 1924 to International Business Machines, IBM for short. This is the same IBM that is known today to many computer users. During the 1980s and 1990s, IBM was a large player in the personal computer market. It was as important as Microsoft is the to the world of computing today. The main term that was used was, “IBM-Compatible.”
A large movement in computer technology was the use of vacuum tubes. In 1904 John Ambrose Fleming invented the first commercial diode vacuum tube. Thomas Edison already discovered this, but discarded the discovery as useless. Before the vacuum tube was discovered, computers were made of gears and switches. Now with the vacuum tube, it acted as a switch turning on and off much faster than standard switches. This also caused less wear and tear on the machine, prolonging the life of the computer, lessening the frequency of repairs.
In 1943 ENIAC (Electronic Numerical Integrator Analyzer and Computer) was built. It was the first all electronic computer, and required so much electricity that when the power was turned on, the lights around Philadelphia dimmed. The ENIAC was used by the United States Military to produce trajectory tables. The ENIAC was able to compute 5,000 additions a second, but it took 2 days to set up these equations. The cost of the ENIAC was $500,000, weighed 30 tons, 100 feet long, and 8 feet high. Inside the ENIAC were 1,500 relays, and 17,468 vacuum tubes. These vacuum tubes consumed 200 kilowatts of electricity, thus causing it’s own circuits to fry. The ENIAC broke down frequently. The problem was that the tubes within the ENIAC produced heat, and turned the ENIAC into an over, causing frequent self-destruction.
In July of 1980, IBM met with Bill Gates to discuss creating an operating system for IBM’s new secret project, a personal computer. IBM almost scrapped the personal computer project in hopes of purchasing Atari, and take over production. But they stuck with their personal computer, and their operating system. On August 12, 1981, IBM released their personal computer, named the IBM PC (this is where the term PC originated from).
The first IBM PC ran on a 4.77 MHz Intel 8088 microprocessor. As for memory, the computer came with 16 kilobytes, which could be expanded to 256k. The computer came with one or two 160k floppy disk drives (5.25 inch). An optional feature was a color monitor. The price tag for this luxurious item was (starting at) $1,565. Today though, it would be the equivalent of $4,000.
For months after the introduction of the IBM PC, Time Magazine named the computer “Man of the Year.” However, IBM wasn’t the only computer on the market. In December of 1983, Apple Computers ran its’ famous “1984” MacIntosh TV commercial. The purpose was to make the commercial eligible for awards during 1984. The commercial itself cost 1.5 million, and ran only once in 1983. It was replayed by new and talk shows, and it made TV history. The next month, Apple Computer ran the same ad, but this time during the NFL Super Bowl, and millions saw their first view of the MacIntosh computer. The commercial showed the IBM world being destroyed by a new machine, the MacIntosh.
And the last big piece of computer history is something that everyone knows, Microsoft Windows operating system. On November 10, 1983, at the Plaza Hotel in New York City, Microsoft announced the release of Microsoft Windows, a new operating system that would provide a graphical user interface (GUI) and multitasking environment for IBM computers. Windows was (summed up) a visual version of DOS. Microsoft promised that the new program would be on the shelf by April 1984. Windows was almost named Interface Manager, but Rowland Hanson (marketing), convinced Microsoft founder Bill Gates that Windows was a better name. Microsoft finally shipped Windows on November 20, 1985, two years after they had initially promised release.
Now you know where computers originated from, and where such companies as Apple, IBM, and Microsoft got their start. As you can see, it wasn’t easy, but they got through it. What would the world be like if Windows was called Interface Manager instead?
The earliest know computer is the abacus, invented by the Chinese in 2600 B.C. Not many people consider this to be a computer, but by definition, it is. One of the more recent early computers was built by Herman Hollerith, who invented a machine that used a system of cards with holes in them. By using these cards he was able to calculate the United State Census. Hollerith’s Computer Tabulating-Recording Company changed its name in 1924 to International Business Machines, IBM for short. This is the same IBM that is known today to many computer users. During the 1980s and 1990s, IBM was a large player in the personal computer market. It was as important as Microsoft is the to the world of computing today. The main term that was used was, “IBM-Compatible.”
A large movement in computer technology was the use of vacuum tubes. In 1904 John Ambrose Fleming invented the first commercial diode vacuum tube. Thomas Edison already discovered this, but discarded the discovery as useless. Before the vacuum tube was discovered, computers were made of gears and switches. Now with the vacuum tube, it acted as a switch turning on and off much faster than standard switches. This also caused less wear and tear on the machine, prolonging the life of the computer, lessening the frequency of repairs.
In 1943 ENIAC (Electronic Numerical Integrator Analyzer and Computer) was built. It was the first all electronic computer, and required so much electricity that when the power was turned on, the lights around Philadelphia dimmed. The ENIAC was used by the United States Military to produce trajectory tables. The ENIAC was able to compute 5,000 additions a second, but it took 2 days to set up these equations. The cost of the ENIAC was $500,000, weighed 30 tons, 100 feet long, and 8 feet high. Inside the ENIAC were 1,500 relays, and 17,468 vacuum tubes. These vacuum tubes consumed 200 kilowatts of electricity, thus causing it’s own circuits to fry. The ENIAC broke down frequently. The problem was that the tubes within the ENIAC produced heat, and turned the ENIAC into an over, causing frequent self-destruction.
In July of 1980, IBM met with Bill Gates to discuss creating an operating system for IBM’s new secret project, a personal computer. IBM almost scrapped the personal computer project in hopes of purchasing Atari, and take over production. But they stuck with their personal computer, and their operating system. On August 12, 1981, IBM released their personal computer, named the IBM PC (this is where the term PC originated from).
The first IBM PC ran on a 4.77 MHz Intel 8088 microprocessor. As for memory, the computer came with 16 kilobytes, which could be expanded to 256k. The computer came with one or two 160k floppy disk drives (5.25 inch). An optional feature was a color monitor. The price tag for this luxurious item was (starting at) $1,565. Today though, it would be the equivalent of $4,000.
For months after the introduction of the IBM PC, Time Magazine named the computer “Man of the Year.” However, IBM wasn’t the only computer on the market. In December of 1983, Apple Computers ran its’ famous “1984” MacIntosh TV commercial. The purpose was to make the commercial eligible for awards during 1984. The commercial itself cost 1.5 million, and ran only once in 1983. It was replayed by new and talk shows, and it made TV history. The next month, Apple Computer ran the same ad, but this time during the NFL Super Bowl, and millions saw their first view of the MacIntosh computer. The commercial showed the IBM world being destroyed by a new machine, the MacIntosh.
And the last big piece of computer history is something that everyone knows, Microsoft Windows operating system. On November 10, 1983, at the Plaza Hotel in New York City, Microsoft announced the release of Microsoft Windows, a new operating system that would provide a graphical user interface (GUI) and multitasking environment for IBM computers. Windows was (summed up) a visual version of DOS. Microsoft promised that the new program would be on the shelf by April 1984. Windows was almost named Interface Manager, but Rowland Hanson (marketing), convinced Microsoft founder Bill Gates that Windows was a better name. Microsoft finally shipped Windows on November 20, 1985, two years after they had initially promised release.
Now you know where computers originated from, and where such companies as Apple, IBM, and Microsoft got their start. As you can see, it wasn’t easy, but they got through it. What would the world be like if Windows was called Interface Manager instead?
Wednesday, February 13, 2008
Computational chemistry
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This article may require cleanup to meet Wikipedia's quality standards.
Please discuss this issue on the talk page or replace this tag with a more specific message.
This article has been tagged since July 2007.
Computational chemistry is a branch of chemistry that uses computers to assist in solving chemical problems. It uses the results of theoretical chemistry, incorporated into efficient computer programs, to calculate the structures and properties of molecules and solids. While its results normally complement the information obtained by chemical experiments, it can in some cases predict hitherto unobserved chemical phenomena. It is widely used in the design of new drugs and materials.
Examples of such properties are structure (i.e. the expected positions of the constituent atoms), absolute and relative (interaction) energies, electronic charge distributions, dipoles and higher multipole moments, vibrational frequencies, reactivity or other spectroscopic quantities, and cross sections for collision with other particles.
The methods employed cover both static and dynamic situations. In all cases the computer time increases rapidly with the size of the system being studied. That system can be a single molecule, a group of molecules or a solid. The methods are thus based on theories which range from highly accurate, but are suitable only for small systems, to very approximate, but suitable for very large systems. The accurate methods are used called ab initio methods, as they are based entirely on theory from first principles. The less accurate methods are called empirical or semi-empirical because some experimental results, often from atoms or related molecules, are used along with the theory.
Contents
[hide]
1 History
2 Concepts
3 Methods
3.1 Ab initio methods
3.2 Density Functional methods
3.3 Semi-empirical and empirical methods
3.4 Molecular mechanics
3.5 Methods for solids
3.6 Chemical dynamics
4 Interpreting molecular wave functions
5 Software packages
6 See also
7 Cited References
8 Other references
9 External links
//
[edit] History
Building on the founding discoveries and theories in the history of quantum mechanics, the first theoretical calculations in chemistry were those of Walter Heitler and Fritz London in 1927. The books that were influential in the early development of computational quantum chemistry include: Linus Pauling and E. Bright Wilson’s 1935 Introduction to Quantum Mechanics – with Applications to Chemistry, Eyring, Walter and Kimball's 1944 Quantum Chemistry, Heitler’s 1945 Elementary Wave Mechanics – with Applications to Quantum Chemistry, and later Coulson's 1952 textbook Valence, each of which served as primary references for chemists in the decades to follow.
With the development of efficient computer technology in the 1940s the solutions of elaborate wave equations for complex atomic systems began to be a realizable objective. In the early 1950s, the first semi-empirical atomic orbital calculations were carried out. Theoretical chemists became extensive users of the early digital computers. A very detailed account of such use in the United Kingdom is given by Smith and Sutcliffe.[1] The first ab initio Hartree-Fock calculations on diatomic molecules were carried out in 1956 at MIT using a basis set of Slater orbitals. For diatomic molecules a systematic study using a minimum basis set and the first calculation with a larger basis set were published by Ransil and Nesbet respectively in 1960.[2] The first polyatomic calculations using Gaussian orbitals were carried out in the late 1950s. The first configuration interaction calculations were carried out in Cambridge on the EDSAC computer in the 1950s using Gaussian orbitals by Boys and coworkers.[3] By 1971, when a bibliography of ab initio calculations was published,[4] the largest molecules included were naphthalene and azulene.[5] [6] Abstracts of many earlier developments in ab initio theory have been published by Schaefer.[7]
In 1964, Hückel method calculations, which are a simple LCAO method for the determination of electron energies of molecular orbitals of π electrons in conjugated hydrocarbon systems, ranging from simple systems such as butadiene and benzene to ovalene with 10 fused six-membered rings , were generated on computers at Berkeley and Oxford.[8] These empirical methods were replaced in the 1960s by semi-empirical methods such as CNDO.[9]
In the early 1970s, efficient ab initio computer programs such as ATMOL, GAUSSIAN, IBMOL, and POLYAYTOM, began to be used to speed up ab initio calculations of molecular orbitals. Of these four programs only GAUSSIAN, massively expanded, is still in use, but many other programs are now in use. At the same time, the methods of molecular mechanics, such as MM2, were developed, primarily by Norman Allinger.[10]
One of the first mentions of the term “computational chemistry” can be found in the 1970 book Computers and Their Role in the Physical Sciences by Sidney Fernbach and Abraham Haskell Taub, where they state “It seems, therefore, that 'computational chemistry' can finally be more and more of a reality.”[11] During the 1970s, widely different methods began to be seen as part of a new emerging discipline of computational chemistry.[12] The Journal of Computational Chemistry was first published in 1980.
[edit] Concepts
The term theoretical chemistry may be defined as a mathematical description of chemistry, whereas computational chemistry is usually used when a mathematical method is sufficiently well developed that it can be automated for implementation on a computer. Note that the words exact and perfect do not appear here, as very few aspects of chemistry can be computed exactly. Almost every aspect of chemistry, however, can be described in a qualitative or approximate quantitative computational scheme.
Molecules consist of nuclei and electrons, so the methods of quantum mechanics apply. Computational chemists often attempt to solve the non-relativistic Schrödinger equation, with relativistic corrections added, although some progress has been made in solving the fully relativistic Schrödinger equation. It is, in principle, possible to solve the Schrödinger equation, in either its time-dependent form or time-independent form as appropriate for the problem in hand, but this in practice is not possible except for very small systems. Therefore, a great number of approximate methods strive to achieve the best trade-off between accuracy and computational cost. Accuracy can always be improved with greater computational cost. Present computational chemistry can routinely accurately calculate the properties of molecules that contain up to about 40 electrons. Errors for energies can be less than 1 kcal/mol. For geometries, bond lengths can be predicted within a few picometres and bond angles within 0.5o. The treatment of larger molecules that contain a few dozen electrons is computationally tractable by approximate methods such as density functional theory (DFT). There is some dispute within the field whether the latter methods are sufficient to describe complex chemical reactions, such as those in biochemistry. Large molecules can be studied by semi-empirical approximate methods. Even larger molecules are treated by classical mechanics methods that are called molecular mechanics.
In theoretical chemistry, chemists, physicists and mathematicians develop algorithms and computer programs to predict atomic and molecular properties and reaction paths for chemical reactions. Computational chemists, in contrast, may simply apply existing computer programs and methodologies to specific chemical questions. There are two different aspects to computational chemistry:
Computational studies can be carried out in order to find a starting point for a laboratory synthesis, or to assist in understanding experimental data, such as the position and source of spectroscopic peaks.
Computational studies can be used to predict the possibility of so far entirely unknown molecules or to explore reaction mechanisms that are not readily studied by experimental means.
Thus computational chemistry can assist the experimental chemist or it can challenge the experimental chemist to find entirely new chemical objects.
Several major areas may be distinguished within computational chemistry:
The prediction of the molecular structure of molecules by the use of the simulation of forces, or more accurate quantum chemical methods, to find stationary points on the energy hypersurface as the position of the nuclei is varied.
Storing and searching for data on chemical entities (see chemical databases).
Identifying correlations between chemical structures and properties (see QSPR and QSAR).
Computational approaches to help in the efficient synthesis of compounds.
Computational approaches to design molecules that interact in specific ways with other molecules (e.g. drug design).
[edit] Methods
A given molecular formula can represent a number of molecular isomers. Each isomer is a local minimum on the energy surface (called the potential energy surface) created from the total energy (electronic energy plus repulsion energy between the nuclei) as a function of the coordinates of all the nuclei. A stationary point is a geometry such that the derivative of the energy with respect to all displacements of the nuclei is zero. A local (energy) minimum is a stationary point where all such displacements lead to an increase in energy. The local minimum that is lowest is called the global minimum and corresponds to the most stable isomer. If there is one particular coordinate change that leads to a decrease in the total energy in both directions, the stationary point is a transition structure and the coordinate is the reaction coordinate. This process of determining stationary points is called geometry optimization.
The determination of molecular structure by geometry optimization became routine only when efficient methods for calculating the first derivatives of the energy with respect to all atomic coordinates became available. Evaluation of the related second derivatives allows the prediction of vibrational frequencies if harmonic motion is assumed. In some ways more importantly it allows the characterisation of stationary points. The frequencies are related to the eigenvalues of the matrix of second derivatives (the Hessian matrix). If the eigenvalues are all positive, then the frequencies are all real and the stationary point is a local minimum. If one eigenvalue is negative (an imaginary frequency), the stationary point is a transition structure. If more than one eigenvalue is negative the stationary point is a more complex one, and usually of little interest. When found, it is necessary to move the search away from it, if we are looking for local minima and transition structures.
The total energy is determined by approximate solutions of the time-dependent Schrödinger equation, usually with no relativistic terms included, and making use of the Born-Oppenheimer approximation which, based on the much higher velocity of the electrons in comparison with the nuclei, allows the separation of electronic and nuclear motions, and simplifies the Schrödinger equation. This leads to evaluating the total energy as a sum of the electronic energy at fixed nuclei positions plus the repulsion energy of the nuclei. A notable exception are certain approaches called direct quantum chemistry, which treat electrons and nuclei on a common footing. Density functional methods and semi-empirical methods are variants on the major theme. For very large systems the relative total energies can be compared using molecular mechanics. The ways of determining the total energy to predict molecular structures are:
[edit] Ab initio methods
Main article: Ab initio quantum chemistry methods
The programs used in computational chemistry are based on many different quantum-chemical methods that solve the molecular Schrödinger equation associated with the molecular Hamiltonian. Methods that do not include any empirical or semi-empirical parameters in their equations - being derived directly from theoretical principles, with no inclusion of experimental data - are called ab initio methods. This does not imply that the solution is an exact one; they are all approximate quantum mechanical calculations. It means that a particular approximation is rigorously defined on first principles (quantum theory) and then solved within an error margin that is qualitatively known beforehand. If numerical iterative methods have to be employed, the aim is to iterate until full machine accuracy is obtained (the best that is possible with a finite word length on the computer, and within the mathematical and/or physical approximations made).
Diagram illustrating various ab initio electronic structure methods in terms of energy.
The simplest type of ab initio electronic structure calculation is the Hartree-Fock (HF) scheme, an extension of molecular orbital theory, in which the correlated electron-electron repulsion is not specifically taken into account; only its average effect is included in the calculation. As the basis set size is increased the energy and wave function tend to a limit called the Hartree-Fock limit. Many types of calculations, known as post-Hartree-Fock methods, begin with a Hartree-Fock calculation and subsequently correct for electron-electron repulsion, referred to also as electronic correlation. As these methods are pushed to the limit, they approach the exact solution of the non-relativistic Schrödinger equation. In order to obtain exact agreement with experiment, it is necessary to include relativistic and spin orbit terms, both of which are only really important for heavy atoms. In all of these approaches, in addition to the choice of method, it is necessary to choose a basis set. This is a set of functions, usually centered on the different atoms in the molecule, which are used to expand the molecular orbitals with the LCAO ansatz. Ab initio methods need to define a level of theory (the method) and a basis set.
The Hartree-Fock wave function is a single configuration or determinant. In some cases, particularly for bond breaking processes, this is quite inadequate and several configurations need to be used. Here the coefficients of the configurations and the coefficients of the basis functions are optimized together.
The total molecular energy can be evaluated as a function of the molecular geometry, in other words the potential energy surface. Such a surface can be used for reaction dynamics. The stationary points of the surface lead to to predictions of different isomers and the transition structures for conversion between isomers, but these can be determined without a full knowledge of the complete surface.
A particularly important objective, called computational thermochemistry, is to calculate thermochemical quantities such as the enthalpy of formation to chemical accuracy. Chemical accuracy is the accuracy required to make realistic chemical predictions and is generally considered to be 1 kcal/mol or 4 kJ/mol. To reach that accuracy in an economic way it is necessary to use a series of post-Hartree-Fock methods and combine the results. These methods are called quantum chemistry composite methods.
[edit] Density Functional methods
Main article: Density functional theory
Density functional theory (DFT) methods are often considered to be ab initio methods for determining the molecular electronic structure, even though many of the most common functionals use parameters derived from empirical data, or from more complex calculations. This means that they could also be called semi-empirical methods. It is best to treat them as a class on their own. In DFT, the total energy is expressed in terms of the total electron density rather than the wave function. In this type of calculation, there is an approximate Hamiltonian and an approximate expression for the total electron density. DFT methods can be very accurate for little computational cost. The drawback is, that unlike ab initio methods, there is no systematic way to improve the methods by improving the form of the functional. Some methods combine the density functional exchange functional with the Hartree-Fock exchange term and are known as hybrid functional methods.
[edit] Semi-empirical and empirical methods
Main article: Semi-empirical quantum chemistry methods
Semi-empirical quantum chemistry methods are based on the Hartree-Fock formalism, but make many approximations and obtain some parameters from empirical data. They are very important in computational chemistry for treating large molecules where the full Hartree-Fock method without the approximations is too expensive. The use of empirical parameters appears to allow some inclusion of correlation effects into the methods.
Semi-empirical methods follow what are often called empirical methods where the two-electron part of the Hamiltonian is not explicitly included. For π-electron systems, this was the Hückel method proposed by Erich Hückel, and for all valence electron systems, the Extended Hückel method proposed by Roald Hoffmann.
[edit] Molecular mechanics
Main article: Molecular mechanics
In many cases, large molecular systems can be modeled successfully while avoiding quantum mechanical calculations entirely. Molecular mechanics simulations, for example, use a single classical expression for the energy of a compound, for instance the harmonic oscillator. All constants appearing in the equations must be obtained beforehand from experimental data or ab initio calculations.
The database of compounds used for parameterization - (the resulting set of parameters and functions is called the force field) - is crucial to the success of molecular mechanics calculations. A force field parameterized against a specific class of molecules, for instance proteins, would be expected to only have any relevance when describing other molecules of the same class.
These methods can be applied to proteins and other large biological molecules, and allow studies of the approach and interaction (docking) of potential drug molecules.
[edit] Methods for solids
Main article: Computational chemical methods in solid state physics
Computational chemical methods can be applied to solid state physics problems. The electronic structure of a crystal is in general described by a band structure, which defines the energies of electron orbitals for each point in the Brillouin zone. Ab initio and semi-empirical calculations yield orbital energies, therefore they can be applied to band structure calculations. Since it is time-consuming to calculate the energy for a molecule, it is even more time-consuming to calculate them for the entire list of points in the Brillouin zone.
[edit] Chemical dynamics
Once the electronic and nuclear variables are separated (within the Born-Oppenheimer representation), in the time-dependent approach, the wave packet corresponding to the nuclear degrees of freedom is propagated via the time evolution operator (physics) associated to the time-dependent Schrödinger equation (for the full molecular Hamiltonian). In the complementary energy-dependent approach, the time-independent Schrödinger equation is solved using the scattering theory formalism. The potential representing the interatomic interaction is given by the potential energy surfaces. In general, the potential energy surfaces are coupled via the vibronic coupling terms.
The most popular methods for propagating the wave packet associated to the molecular geometry are
the split operator technique,
the Multi-Configuration Time-Dependent Hartree method (MCTDH),
the semiclassical method.
Molecular dynamics (MD) examines (using Newton's laws of motion) the time-dependent behavior of systems, including vibrations or Brownian motion, using a classical mechanical description. MD combined with density functional theory leads to the Car-Parrinello method.
[edit] Interpreting molecular wave functions
The Atoms in Molecules model developed by Richard Bader was developed in order to effectively link the quantum mechanical picture of a molecule, as an electronic wavefunction, to chemically useful older models such as the theory of Lewis pairs and the valence bond model. Bader has demonstrated that these empirically useful models are connected with the topology of the quantum charge density. This method improves on the use of Mulliken population analysis.
[edit] Software packages
There are many self-sufficient software packages used by computational chemists. Some include many methods covering a wide range, while others concentrating on a very specific range or even a single method. Details of most of them can be found in:-
Quantum chemistry computer programs supporting several methods.
Density functional theory programs.
Molecular mechanics programs.
Semi-empirical programs.
Solid state system programs with periodic boundary conditions.
Valence Bond programs.
Jump to: navigation, search
This article may require cleanup to meet Wikipedia's quality standards.
Please discuss this issue on the talk page or replace this tag with a more specific message.
This article has been tagged since July 2007.
Computational chemistry is a branch of chemistry that uses computers to assist in solving chemical problems. It uses the results of theoretical chemistry, incorporated into efficient computer programs, to calculate the structures and properties of molecules and solids. While its results normally complement the information obtained by chemical experiments, it can in some cases predict hitherto unobserved chemical phenomena. It is widely used in the design of new drugs and materials.
Examples of such properties are structure (i.e. the expected positions of the constituent atoms), absolute and relative (interaction) energies, electronic charge distributions, dipoles and higher multipole moments, vibrational frequencies, reactivity or other spectroscopic quantities, and cross sections for collision with other particles.
The methods employed cover both static and dynamic situations. In all cases the computer time increases rapidly with the size of the system being studied. That system can be a single molecule, a group of molecules or a solid. The methods are thus based on theories which range from highly accurate, but are suitable only for small systems, to very approximate, but suitable for very large systems. The accurate methods are used called ab initio methods, as they are based entirely on theory from first principles. The less accurate methods are called empirical or semi-empirical because some experimental results, often from atoms or related molecules, are used along with the theory.
Contents
[hide]
1 History
2 Concepts
3 Methods
3.1 Ab initio methods
3.2 Density Functional methods
3.3 Semi-empirical and empirical methods
3.4 Molecular mechanics
3.5 Methods for solids
3.6 Chemical dynamics
4 Interpreting molecular wave functions
5 Software packages
6 See also
7 Cited References
8 Other references
9 External links
//
[edit] History
Building on the founding discoveries and theories in the history of quantum mechanics, the first theoretical calculations in chemistry were those of Walter Heitler and Fritz London in 1927. The books that were influential in the early development of computational quantum chemistry include: Linus Pauling and E. Bright Wilson’s 1935 Introduction to Quantum Mechanics – with Applications to Chemistry, Eyring, Walter and Kimball's 1944 Quantum Chemistry, Heitler’s 1945 Elementary Wave Mechanics – with Applications to Quantum Chemistry, and later Coulson's 1952 textbook Valence, each of which served as primary references for chemists in the decades to follow.
With the development of efficient computer technology in the 1940s the solutions of elaborate wave equations for complex atomic systems began to be a realizable objective. In the early 1950s, the first semi-empirical atomic orbital calculations were carried out. Theoretical chemists became extensive users of the early digital computers. A very detailed account of such use in the United Kingdom is given by Smith and Sutcliffe.[1] The first ab initio Hartree-Fock calculations on diatomic molecules were carried out in 1956 at MIT using a basis set of Slater orbitals. For diatomic molecules a systematic study using a minimum basis set and the first calculation with a larger basis set were published by Ransil and Nesbet respectively in 1960.[2] The first polyatomic calculations using Gaussian orbitals were carried out in the late 1950s. The first configuration interaction calculations were carried out in Cambridge on the EDSAC computer in the 1950s using Gaussian orbitals by Boys and coworkers.[3] By 1971, when a bibliography of ab initio calculations was published,[4] the largest molecules included were naphthalene and azulene.[5] [6] Abstracts of many earlier developments in ab initio theory have been published by Schaefer.[7]
In 1964, Hückel method calculations, which are a simple LCAO method for the determination of electron energies of molecular orbitals of π electrons in conjugated hydrocarbon systems, ranging from simple systems such as butadiene and benzene to ovalene with 10 fused six-membered rings , were generated on computers at Berkeley and Oxford.[8] These empirical methods were replaced in the 1960s by semi-empirical methods such as CNDO.[9]
In the early 1970s, efficient ab initio computer programs such as ATMOL, GAUSSIAN, IBMOL, and POLYAYTOM, began to be used to speed up ab initio calculations of molecular orbitals. Of these four programs only GAUSSIAN, massively expanded, is still in use, but many other programs are now in use. At the same time, the methods of molecular mechanics, such as MM2, were developed, primarily by Norman Allinger.[10]
One of the first mentions of the term “computational chemistry” can be found in the 1970 book Computers and Their Role in the Physical Sciences by Sidney Fernbach and Abraham Haskell Taub, where they state “It seems, therefore, that 'computational chemistry' can finally be more and more of a reality.”[11] During the 1970s, widely different methods began to be seen as part of a new emerging discipline of computational chemistry.[12] The Journal of Computational Chemistry was first published in 1980.
[edit] Concepts
The term theoretical chemistry may be defined as a mathematical description of chemistry, whereas computational chemistry is usually used when a mathematical method is sufficiently well developed that it can be automated for implementation on a computer. Note that the words exact and perfect do not appear here, as very few aspects of chemistry can be computed exactly. Almost every aspect of chemistry, however, can be described in a qualitative or approximate quantitative computational scheme.
Molecules consist of nuclei and electrons, so the methods of quantum mechanics apply. Computational chemists often attempt to solve the non-relativistic Schrödinger equation, with relativistic corrections added, although some progress has been made in solving the fully relativistic Schrödinger equation. It is, in principle, possible to solve the Schrödinger equation, in either its time-dependent form or time-independent form as appropriate for the problem in hand, but this in practice is not possible except for very small systems. Therefore, a great number of approximate methods strive to achieve the best trade-off between accuracy and computational cost. Accuracy can always be improved with greater computational cost. Present computational chemistry can routinely accurately calculate the properties of molecules that contain up to about 40 electrons. Errors for energies can be less than 1 kcal/mol. For geometries, bond lengths can be predicted within a few picometres and bond angles within 0.5o. The treatment of larger molecules that contain a few dozen electrons is computationally tractable by approximate methods such as density functional theory (DFT). There is some dispute within the field whether the latter methods are sufficient to describe complex chemical reactions, such as those in biochemistry. Large molecules can be studied by semi-empirical approximate methods. Even larger molecules are treated by classical mechanics methods that are called molecular mechanics.
In theoretical chemistry, chemists, physicists and mathematicians develop algorithms and computer programs to predict atomic and molecular properties and reaction paths for chemical reactions. Computational chemists, in contrast, may simply apply existing computer programs and methodologies to specific chemical questions. There are two different aspects to computational chemistry:
Computational studies can be carried out in order to find a starting point for a laboratory synthesis, or to assist in understanding experimental data, such as the position and source of spectroscopic peaks.
Computational studies can be used to predict the possibility of so far entirely unknown molecules or to explore reaction mechanisms that are not readily studied by experimental means.
Thus computational chemistry can assist the experimental chemist or it can challenge the experimental chemist to find entirely new chemical objects.
Several major areas may be distinguished within computational chemistry:
The prediction of the molecular structure of molecules by the use of the simulation of forces, or more accurate quantum chemical methods, to find stationary points on the energy hypersurface as the position of the nuclei is varied.
Storing and searching for data on chemical entities (see chemical databases).
Identifying correlations between chemical structures and properties (see QSPR and QSAR).
Computational approaches to help in the efficient synthesis of compounds.
Computational approaches to design molecules that interact in specific ways with other molecules (e.g. drug design).
[edit] Methods
A given molecular formula can represent a number of molecular isomers. Each isomer is a local minimum on the energy surface (called the potential energy surface) created from the total energy (electronic energy plus repulsion energy between the nuclei) as a function of the coordinates of all the nuclei. A stationary point is a geometry such that the derivative of the energy with respect to all displacements of the nuclei is zero. A local (energy) minimum is a stationary point where all such displacements lead to an increase in energy. The local minimum that is lowest is called the global minimum and corresponds to the most stable isomer. If there is one particular coordinate change that leads to a decrease in the total energy in both directions, the stationary point is a transition structure and the coordinate is the reaction coordinate. This process of determining stationary points is called geometry optimization.
The determination of molecular structure by geometry optimization became routine only when efficient methods for calculating the first derivatives of the energy with respect to all atomic coordinates became available. Evaluation of the related second derivatives allows the prediction of vibrational frequencies if harmonic motion is assumed. In some ways more importantly it allows the characterisation of stationary points. The frequencies are related to the eigenvalues of the matrix of second derivatives (the Hessian matrix). If the eigenvalues are all positive, then the frequencies are all real and the stationary point is a local minimum. If one eigenvalue is negative (an imaginary frequency), the stationary point is a transition structure. If more than one eigenvalue is negative the stationary point is a more complex one, and usually of little interest. When found, it is necessary to move the search away from it, if we are looking for local minima and transition structures.
The total energy is determined by approximate solutions of the time-dependent Schrödinger equation, usually with no relativistic terms included, and making use of the Born-Oppenheimer approximation which, based on the much higher velocity of the electrons in comparison with the nuclei, allows the separation of electronic and nuclear motions, and simplifies the Schrödinger equation. This leads to evaluating the total energy as a sum of the electronic energy at fixed nuclei positions plus the repulsion energy of the nuclei. A notable exception are certain approaches called direct quantum chemistry, which treat electrons and nuclei on a common footing. Density functional methods and semi-empirical methods are variants on the major theme. For very large systems the relative total energies can be compared using molecular mechanics. The ways of determining the total energy to predict molecular structures are:
[edit] Ab initio methods
Main article: Ab initio quantum chemistry methods
The programs used in computational chemistry are based on many different quantum-chemical methods that solve the molecular Schrödinger equation associated with the molecular Hamiltonian. Methods that do not include any empirical or semi-empirical parameters in their equations - being derived directly from theoretical principles, with no inclusion of experimental data - are called ab initio methods. This does not imply that the solution is an exact one; they are all approximate quantum mechanical calculations. It means that a particular approximation is rigorously defined on first principles (quantum theory) and then solved within an error margin that is qualitatively known beforehand. If numerical iterative methods have to be employed, the aim is to iterate until full machine accuracy is obtained (the best that is possible with a finite word length on the computer, and within the mathematical and/or physical approximations made).
Diagram illustrating various ab initio electronic structure methods in terms of energy.
The simplest type of ab initio electronic structure calculation is the Hartree-Fock (HF) scheme, an extension of molecular orbital theory, in which the correlated electron-electron repulsion is not specifically taken into account; only its average effect is included in the calculation. As the basis set size is increased the energy and wave function tend to a limit called the Hartree-Fock limit. Many types of calculations, known as post-Hartree-Fock methods, begin with a Hartree-Fock calculation and subsequently correct for electron-electron repulsion, referred to also as electronic correlation. As these methods are pushed to the limit, they approach the exact solution of the non-relativistic Schrödinger equation. In order to obtain exact agreement with experiment, it is necessary to include relativistic and spin orbit terms, both of which are only really important for heavy atoms. In all of these approaches, in addition to the choice of method, it is necessary to choose a basis set. This is a set of functions, usually centered on the different atoms in the molecule, which are used to expand the molecular orbitals with the LCAO ansatz. Ab initio methods need to define a level of theory (the method) and a basis set.
The Hartree-Fock wave function is a single configuration or determinant. In some cases, particularly for bond breaking processes, this is quite inadequate and several configurations need to be used. Here the coefficients of the configurations and the coefficients of the basis functions are optimized together.
The total molecular energy can be evaluated as a function of the molecular geometry, in other words the potential energy surface. Such a surface can be used for reaction dynamics. The stationary points of the surface lead to to predictions of different isomers and the transition structures for conversion between isomers, but these can be determined without a full knowledge of the complete surface.
A particularly important objective, called computational thermochemistry, is to calculate thermochemical quantities such as the enthalpy of formation to chemical accuracy. Chemical accuracy is the accuracy required to make realistic chemical predictions and is generally considered to be 1 kcal/mol or 4 kJ/mol. To reach that accuracy in an economic way it is necessary to use a series of post-Hartree-Fock methods and combine the results. These methods are called quantum chemistry composite methods.
[edit] Density Functional methods
Main article: Density functional theory
Density functional theory (DFT) methods are often considered to be ab initio methods for determining the molecular electronic structure, even though many of the most common functionals use parameters derived from empirical data, or from more complex calculations. This means that they could also be called semi-empirical methods. It is best to treat them as a class on their own. In DFT, the total energy is expressed in terms of the total electron density rather than the wave function. In this type of calculation, there is an approximate Hamiltonian and an approximate expression for the total electron density. DFT methods can be very accurate for little computational cost. The drawback is, that unlike ab initio methods, there is no systematic way to improve the methods by improving the form of the functional. Some methods combine the density functional exchange functional with the Hartree-Fock exchange term and are known as hybrid functional methods.
[edit] Semi-empirical and empirical methods
Main article: Semi-empirical quantum chemistry methods
Semi-empirical quantum chemistry methods are based on the Hartree-Fock formalism, but make many approximations and obtain some parameters from empirical data. They are very important in computational chemistry for treating large molecules where the full Hartree-Fock method without the approximations is too expensive. The use of empirical parameters appears to allow some inclusion of correlation effects into the methods.
Semi-empirical methods follow what are often called empirical methods where the two-electron part of the Hamiltonian is not explicitly included. For π-electron systems, this was the Hückel method proposed by Erich Hückel, and for all valence electron systems, the Extended Hückel method proposed by Roald Hoffmann.
[edit] Molecular mechanics
Main article: Molecular mechanics
In many cases, large molecular systems can be modeled successfully while avoiding quantum mechanical calculations entirely. Molecular mechanics simulations, for example, use a single classical expression for the energy of a compound, for instance the harmonic oscillator. All constants appearing in the equations must be obtained beforehand from experimental data or ab initio calculations.
The database of compounds used for parameterization - (the resulting set of parameters and functions is called the force field) - is crucial to the success of molecular mechanics calculations. A force field parameterized against a specific class of molecules, for instance proteins, would be expected to only have any relevance when describing other molecules of the same class.
These methods can be applied to proteins and other large biological molecules, and allow studies of the approach and interaction (docking) of potential drug molecules.
[edit] Methods for solids
Main article: Computational chemical methods in solid state physics
Computational chemical methods can be applied to solid state physics problems. The electronic structure of a crystal is in general described by a band structure, which defines the energies of electron orbitals for each point in the Brillouin zone. Ab initio and semi-empirical calculations yield orbital energies, therefore they can be applied to band structure calculations. Since it is time-consuming to calculate the energy for a molecule, it is even more time-consuming to calculate them for the entire list of points in the Brillouin zone.
[edit] Chemical dynamics
Once the electronic and nuclear variables are separated (within the Born-Oppenheimer representation), in the time-dependent approach, the wave packet corresponding to the nuclear degrees of freedom is propagated via the time evolution operator (physics) associated to the time-dependent Schrödinger equation (for the full molecular Hamiltonian). In the complementary energy-dependent approach, the time-independent Schrödinger equation is solved using the scattering theory formalism. The potential representing the interatomic interaction is given by the potential energy surfaces. In general, the potential energy surfaces are coupled via the vibronic coupling terms.
The most popular methods for propagating the wave packet associated to the molecular geometry are
the split operator technique,
the Multi-Configuration Time-Dependent Hartree method (MCTDH),
the semiclassical method.
Molecular dynamics (MD) examines (using Newton's laws of motion) the time-dependent behavior of systems, including vibrations or Brownian motion, using a classical mechanical description. MD combined with density functional theory leads to the Car-Parrinello method.
[edit] Interpreting molecular wave functions
The Atoms in Molecules model developed by Richard Bader was developed in order to effectively link the quantum mechanical picture of a molecule, as an electronic wavefunction, to chemically useful older models such as the theory of Lewis pairs and the valence bond model. Bader has demonstrated that these empirically useful models are connected with the topology of the quantum charge density. This method improves on the use of Mulliken population analysis.
[edit] Software packages
There are many self-sufficient software packages used by computational chemists. Some include many methods covering a wide range, while others concentrating on a very specific range or even a single method. Details of most of them can be found in:-
Quantum chemistry computer programs supporting several methods.
Density functional theory programs.
Molecular mechanics programs.
Semi-empirical programs.
Solid state system programs with periodic boundary conditions.
Valence Bond programs.
Tuesday, February 12, 2008
History of the Computer Industry in America
Only once in a lifetime will a new invention come about to touch
every aspect of our lives. Such a device that changes the way we work,
live, and play is a special one, indeed. A machine that has done all
this and more now exists in nearly every business in the U.S. and one
out of every two households (Hall, 156). This incredible invention is
the computer. The electronic computer has been around for over a
half-century, but its ancestors have been around for 2000 years.
However, only in the last 40 years has it changed the American society.
>From the first wooden abacus to the latest high-speed microprocessor,
the computer has changed nearly every aspect of peopleÕs lives for the
better.
The very earliest existence of the modern day computerÕs
ancestor is the abacus. These date back to almost 2000 years ago. It
is simply a wooden rack holding parallel wires on which beads are
strung. When these beads are moved along the wire according to
"programming" rules that the user must memorize, all ordinary arithmetic
operations can be performed (Soma, 14). The next innovation in
computers took place in 1694 when Blaise Pascal invented the first
Òdigital calculating machineÓ. It could only add numbers and they had
to be entered by turning dials. It was designed to help PascalÕs father
who was a tax collector (Soma, 32).
In the early 1800Õs, a mathematics professor named Charles
Babbage designed an automatic calculation machine. It was steam powered
and could store up to 1000 50-digit numbers. Built in to his machine
were operations that included everything a modern general-purpose
computer would need. It was programmed by--and stored data on--cards
with holes punched in them, appropriately called ÒpunchcardsÓ. His
inventions were failures for the most part because of the lack of
precision machining techniques used at the time and the lack of demand
for such a device (Soma, 46).
After Babbage, people began to lose interest in computers.
However, between 1850 and 1900 there were great advances in mathematics
and physics that began to rekindle the interest (Osborne, 45). Many of
these new advances involved complex calculations and formulas that were
very time consuming for human calculation. The first major use for a
computer in the U.S. was during the 1890 census. Two men, Herman
Hollerith and James Powers, developed a new punched-card system that
could automatically read information on cards without human intervention
(Gulliver, 82). Since the population of the U.S. was increasing so
fast, the computer was an essential tool in tabulating the totals.
These advantages were noted by commercial industries and soon
led to the development of improved punch-card business-machine systems
by International Business Machines (IBM), Remington-Rand, Burroughs, and
other corporations. By modern standards the punched-card machines were
slow, typically processing from 50 to 250 cards per minute, with each
card holding up to 80 digits. At the time, however, punched cards were
an enormous step forward; they provided a means of input, output, and
memory storage on a massive scale. For more than 50 years following
their first use, punched-card machines did the bulk of the world's
business computing and a good portion of the computing work in science
(Chposky, 73).
By the late 1930s punched-card machine techniques had become so
well established and reliable that Howard Hathaway Aiken, in
collaboration with engineers at IBM, undertook construction of a large
automatic digital computer based on standard IBM electromechanical
parts. Aiken's machine, called the Harvard Mark I, handled 23-digit
numbers and could perform all four arithmetic operations. Also, it had
special built-in programs to handle logarithms and trigonometric
functions. The Mark I was controlled from prepunched paper tape.
Output was by card punch and electric typewriter. It was slow,
requiring 3 to 5 seconds for a multiplication, but it was fully
automatic and could complete long computations without human
intervention (Chposky, 103).
The outbreak of World War II produced a desperate need for
computing capability, especially for the military. New weapons systems
were produced which needed trajectory tables and other essential data.
In 1942, John P. Eckert, John W. Mauchley, and their associates at the
University of Pennsylvania decided to build a high-speed electronic
computer to do the job. This machine became known as ENIAC, for
"Electrical Numerical Integrator And Calculator". It could multiply two
numbers at the rate of 300 products per second, by finding the value of
each product from a multiplication table stored in its memory. ENIAC was
thus about 1,000 times faster than the previous generation of computers
(Dolotta, 47).
ENIAC used 18,000 standard vacuum tubes, occupied 1800 square
feet of floor space, and used about 180,000 watts of electricity. It
used punched-card input and output. The ENIAC was very difficult to
program because one had to essentially re-wire it to perform whatever
task he wanted the computer to do. It was, however, efficient in
handling the particular programs for which it had been designed. ENIAC
is generally accepted as the first successful high-speed electronic
digital computer and was used in many applications from 1946 to 1955
(Dolotta, 50).
Mathematician John von Neumann was very interested in the ENIAC.
In 1945 he undertook a theoretical study of computation that
demonstrated that a computer could have a very simple and yet be able to
execute any kind of computation effectively by means of proper
programmed control without the need for any changes in hardware. Von
Neumann came up with incredible ideas for methods of building and
organizing practical, fast computers. These ideas, which came to be
referred to as the stored-program technique, became fundamental for
future generations of high-speed digital computers and were universally
adopted (Hall, 73).
The first wave of modern programmed electronic computers to take
advantage of these improvements appeared in 1947. This group included
computers using random access memory (RAM), which is a memory designed
to give almost constant access to any particular piece of information
(Hall, 75). These machines had punched-card or punched-tape input and
output devices and RAMs of 1000-word capacity. Physically, they were
much more compact than ENIAC: some were about the size of a grand piano
and required 2500 small electron tubes. This was quite an improvement
over the earlier machines. The first-generation stored-program
computers required considerable maintenance, usually attained 70% to 80%
reliable operation, and were used for 8 to 12 years. Typically, they
were programmed directly in machine language, although by the mid-1950s
progress had been made in several aspects of advanced programming. This
group of machines included EDVAC and UNIVAC, the first commercially
available computers (Hazewindus, 102).
The UNIVAC was developed by John W. Mauchley and John Eckert,
Jr. in the 1950Õs. Together they had formed the Mauchley-Eckert
Computer Corporation, AmericaÕs first computer company in the 1940Õs.
During the development of the UNIVAC, they began to run short on funds
and sold their company to the larger Remington-Rand Corporation.
Eventually they built a working UNIVAC computer. It was delivered to
the U.S. Census Bureau in 1951 where it was used to help tabulate the
U.S. population (Hazewindus, 124).
Early in the 1950s two important engineering discoveries changed
the electronic computer field. The first computers were made with
vacuum tubes, but by the late 1950Õs computers were being made out of
transistors, which were smaller, less expensive, more reliable, and more
efficient (Shallis, 40). In 1959, Robert Noyce, a physicist at the
Fairchild Semiconductor Corporation, invented the integrated circuit, a
tiny chip of silicon that contained an entire electronic circuit. Gone
was the bulky, unreliable, but fast machine; now computers began to
become more compact, more reliable and have more capacity (Shallis, 49).
These new technical discoveries rapidly found their way into new
models of digital computers. Memory storage capacities increased 800%
in commercially available machines by the early 1960s and speeds
increased by an equally large margin. These machines were very
expensive to purchase or to rent and were especially expensive to
operate because of the cost of hiring programmers to perform the complex
operations the computers ran. Such computers were typically found in
large computer centers--operated by industry, government, and private
laboratories--staffed with many programmers and support personnel
(Rogers, 77). By 1956, 76 of IBMÕs large computer mainframes were in
use, compared with only 46 UNIVACÕs (Chposky, 125).
In the 1960s efforts to design and develop the fastest possible
computers with the greatest capacity reached a turning point with the
completion of the LARC machine for Livermore Radiation Laboratories by
the Sperry-Rand Corporation, and the Stretch computer by IBM. The LARC
had a core memory of 98,000 words and multiplied in 10 microseconds.
Stretch was provided with several ranks of memory having slower access
for the ranks of greater capacity, the fastest access time being less
than 1 microseconds and the total capacity in the vicinity of 100
million words (Chposky, 147).
During this time the major computer manufacturers began to offer
a range of computer capabilities, as well as various computer-related
equipment. These included input means such as consoles and card
feeders; output means such as page printers, cathode-ray-tube displays,
and graphing devices; and optional magnetic-tape and magnetic-disk file
storage. These found wide use in business for such applications as
accounting, payroll, inventory control, ordering supplies, and billing.
Central processing units (CPUs) for such purposes did not need to be
very fast arithmetically and were primarily used to access large amounts
of records on file. The greatest number of computer systems were
delivered for the larger applications, such as in hospitals for keeping
track of patient records, medications, and treatments given. They were
also used in automated library systems and in database systems such as
the Chemical Abstracts system, where computer records now on file cover
nearly all known chemical compounds (Rogers, 98).
The trend during the 1970s was, to some extent, away from
extremely powerful, centralized computational centers and toward a
broader range of applications for less-costly computer systems. Most
continuous-process manufacturing, such as petroleum refining and
electrical-power distribution systems, began using computers of
relatively modest capability for controlling and regulating their
activities. In the 1960s the programming of applications problems was
an obstacle to the self-sufficiency of moderate-sized on-site computer
installations, but great advances in applications programming languages
removed these obstacles. Applications languages became available for
controlling a great range of manufacturing processes, for computer
operation of machine tools, and for many other tasks (Osborne, 146). In
1971 Marcian E. Hoff, Jr., an engineer at the Intel Corporation,
invented the microprocessor and another stage in the deveopment of the
computer began (Shallis, 121).
A new revolution in computer hardware was now well under way,
involving miniaturization of computer-logic circuitry and of component
manufacture by what are called large-scale integration techniques. In
the 1950s it was realized that "scaling down" the size of electronic
digital computer circuits and parts would increase speed and efficiency
and improve performance. However, at that time the manufacturing
methods were not good enough to accomplish such a task. About 1960
photoprinting of conductive circuit boards to eliminate wiring became
highly developed. Then it became possible to build resistors and
capacitors into the circuitry by photographic means (Rogers, 142). In
the 1970s entire assemblies, such as adders, shifting registers, and
counters, became available on tiny chips of silicon. In the 1980s very
large scale integration (VLSI), in which hundreds of thousands of
transistors are placed on a single chip, became increasingly common.
Many companies, some new to the computer field, introduced in the 1970s
programmable minicomputers supplied with software packages. The
size-reduction trend continued with the introduction of personal
computers, which are programmable machines small enough and inexpensive
enough to be purchased and used by individuals (Rogers, 153).
One of the first of such machines was introduced in January
1975. Popular Electronics magazine provided plans that would allow any
electronics wizard to build his own small, programmable computer for
about $380 (Rose, 32). The computer was called the ÒAltair 8800Ó. Its
programming involved pushing buttons and flipping switches on the front
of the box. It didnÕt include a monitor or keyboard, and its
applications were very limited (Jacobs, 53). Even though, many orders
came in for it and several famous owners of computer and software
manufacturing companies got their start in computing through the Altair.
For example, Steve Jobs and Steve Wozniak, founders of Apple Computer,
built a much cheaper, yet more productive version of the Altair and
turned their hobby into a business (Fluegelman, 16).
After the introduction of the Altair 8800, the personal computer
industry became a fierce battleground of competition. IBM had been the
computer industry standard for well over a half-century. They held
their position as the standard when they introduced their first personal
computer, the IBM Model 60 in 1975 (Chposky, 156). However, the newly
formed Apple Computer company was releasing its own personal computer,
the Apple II (The Apple I was the first computer designed by Jobs and
Wozniak in WozniakÕs garage, which was not produced on a wide scale).
Software was needed to run the computers as well. Microsoft developed a
Disk Operating System (MS-DOS) for the IBM computer while Apple
developed its own software system (Rose, 37). Because Microsoft had now
set the software standard for IBMs, every software manufacturer had to
make their software compatible with MicrosoftÕs. This would lead to
huge profits for Microsoft (Cringley, 163).
The main goal of the computer manufacturers was to make the
computer as affordable as possible while increasing speed, reliability,
and capacity. Nearly every computer manufacturer accomplished this and
computers popped up everywhere. Computers were in businesses keeping
track of inventories. Computers were in colleges aiding students in
research. Computers were in laboratories making complex calculations at
high speeds for scientists and physicists. The computer had made its
mark everywhere in society and built up a huge industry (Cringley, 174).
The future is promising for the computer industry and its
technology. The speed of processors is expected to double every year
and a half in the coming years. As manufacturing techniques are further
perfected the prices of computer systems are expected to steadily fall.
However, since the microprocessor technology will be increasing, itÕs
higher costs will offset the drop in price of older processors. In other
words, the price of a new computer will stay about the same from year to
year, but technology will steadily increase (Zachary, 42)
Since the end of World War II, the computer industry has grown
from a standing start into one of the biggest and most profitable
industries in the United States. It now comprises thousands of
companies, making everything from multi-million dollar high-speed
supercomputers to printout paper and floppy disks. It employs millions
of people and generates tens of billions of dollars in sales each year
(Malone, 192). Surely, the computer has impacted every aspect of
peopleÕs lives. It has affected the way people work and play. It has
made everyoneÕs life easier by doing difficult work for people. The computer truly is one of the most incredible inventions in history.
every aspect of our lives. Such a device that changes the way we work,
live, and play is a special one, indeed. A machine that has done all
this and more now exists in nearly every business in the U.S. and one
out of every two households (Hall, 156). This incredible invention is
the computer. The electronic computer has been around for over a
half-century, but its ancestors have been around for 2000 years.
However, only in the last 40 years has it changed the American society.
>From the first wooden abacus to the latest high-speed microprocessor,
the computer has changed nearly every aspect of peopleÕs lives for the
better.
The very earliest existence of the modern day computerÕs
ancestor is the abacus. These date back to almost 2000 years ago. It
is simply a wooden rack holding parallel wires on which beads are
strung. When these beads are moved along the wire according to
"programming" rules that the user must memorize, all ordinary arithmetic
operations can be performed (Soma, 14). The next innovation in
computers took place in 1694 when Blaise Pascal invented the first
Òdigital calculating machineÓ. It could only add numbers and they had
to be entered by turning dials. It was designed to help PascalÕs father
who was a tax collector (Soma, 32).
In the early 1800Õs, a mathematics professor named Charles
Babbage designed an automatic calculation machine. It was steam powered
and could store up to 1000 50-digit numbers. Built in to his machine
were operations that included everything a modern general-purpose
computer would need. It was programmed by--and stored data on--cards
with holes punched in them, appropriately called ÒpunchcardsÓ. His
inventions were failures for the most part because of the lack of
precision machining techniques used at the time and the lack of demand
for such a device (Soma, 46).
After Babbage, people began to lose interest in computers.
However, between 1850 and 1900 there were great advances in mathematics
and physics that began to rekindle the interest (Osborne, 45). Many of
these new advances involved complex calculations and formulas that were
very time consuming for human calculation. The first major use for a
computer in the U.S. was during the 1890 census. Two men, Herman
Hollerith and James Powers, developed a new punched-card system that
could automatically read information on cards without human intervention
(Gulliver, 82). Since the population of the U.S. was increasing so
fast, the computer was an essential tool in tabulating the totals.
These advantages were noted by commercial industries and soon
led to the development of improved punch-card business-machine systems
by International Business Machines (IBM), Remington-Rand, Burroughs, and
other corporations. By modern standards the punched-card machines were
slow, typically processing from 50 to 250 cards per minute, with each
card holding up to 80 digits. At the time, however, punched cards were
an enormous step forward; they provided a means of input, output, and
memory storage on a massive scale. For more than 50 years following
their first use, punched-card machines did the bulk of the world's
business computing and a good portion of the computing work in science
(Chposky, 73).
By the late 1930s punched-card machine techniques had become so
well established and reliable that Howard Hathaway Aiken, in
collaboration with engineers at IBM, undertook construction of a large
automatic digital computer based on standard IBM electromechanical
parts. Aiken's machine, called the Harvard Mark I, handled 23-digit
numbers and could perform all four arithmetic operations. Also, it had
special built-in programs to handle logarithms and trigonometric
functions. The Mark I was controlled from prepunched paper tape.
Output was by card punch and electric typewriter. It was slow,
requiring 3 to 5 seconds for a multiplication, but it was fully
automatic and could complete long computations without human
intervention (Chposky, 103).
The outbreak of World War II produced a desperate need for
computing capability, especially for the military. New weapons systems
were produced which needed trajectory tables and other essential data.
In 1942, John P. Eckert, John W. Mauchley, and their associates at the
University of Pennsylvania decided to build a high-speed electronic
computer to do the job. This machine became known as ENIAC, for
"Electrical Numerical Integrator And Calculator". It could multiply two
numbers at the rate of 300 products per second, by finding the value of
each product from a multiplication table stored in its memory. ENIAC was
thus about 1,000 times faster than the previous generation of computers
(Dolotta, 47).
ENIAC used 18,000 standard vacuum tubes, occupied 1800 square
feet of floor space, and used about 180,000 watts of electricity. It
used punched-card input and output. The ENIAC was very difficult to
program because one had to essentially re-wire it to perform whatever
task he wanted the computer to do. It was, however, efficient in
handling the particular programs for which it had been designed. ENIAC
is generally accepted as the first successful high-speed electronic
digital computer and was used in many applications from 1946 to 1955
(Dolotta, 50).
Mathematician John von Neumann was very interested in the ENIAC.
In 1945 he undertook a theoretical study of computation that
demonstrated that a computer could have a very simple and yet be able to
execute any kind of computation effectively by means of proper
programmed control without the need for any changes in hardware. Von
Neumann came up with incredible ideas for methods of building and
organizing practical, fast computers. These ideas, which came to be
referred to as the stored-program technique, became fundamental for
future generations of high-speed digital computers and were universally
adopted (Hall, 73).
The first wave of modern programmed electronic computers to take
advantage of these improvements appeared in 1947. This group included
computers using random access memory (RAM), which is a memory designed
to give almost constant access to any particular piece of information
(Hall, 75). These machines had punched-card or punched-tape input and
output devices and RAMs of 1000-word capacity. Physically, they were
much more compact than ENIAC: some were about the size of a grand piano
and required 2500 small electron tubes. This was quite an improvement
over the earlier machines. The first-generation stored-program
computers required considerable maintenance, usually attained 70% to 80%
reliable operation, and were used for 8 to 12 years. Typically, they
were programmed directly in machine language, although by the mid-1950s
progress had been made in several aspects of advanced programming. This
group of machines included EDVAC and UNIVAC, the first commercially
available computers (Hazewindus, 102).
The UNIVAC was developed by John W. Mauchley and John Eckert,
Jr. in the 1950Õs. Together they had formed the Mauchley-Eckert
Computer Corporation, AmericaÕs first computer company in the 1940Õs.
During the development of the UNIVAC, they began to run short on funds
and sold their company to the larger Remington-Rand Corporation.
Eventually they built a working UNIVAC computer. It was delivered to
the U.S. Census Bureau in 1951 where it was used to help tabulate the
U.S. population (Hazewindus, 124).
Early in the 1950s two important engineering discoveries changed
the electronic computer field. The first computers were made with
vacuum tubes, but by the late 1950Õs computers were being made out of
transistors, which were smaller, less expensive, more reliable, and more
efficient (Shallis, 40). In 1959, Robert Noyce, a physicist at the
Fairchild Semiconductor Corporation, invented the integrated circuit, a
tiny chip of silicon that contained an entire electronic circuit. Gone
was the bulky, unreliable, but fast machine; now computers began to
become more compact, more reliable and have more capacity (Shallis, 49).
These new technical discoveries rapidly found their way into new
models of digital computers. Memory storage capacities increased 800%
in commercially available machines by the early 1960s and speeds
increased by an equally large margin. These machines were very
expensive to purchase or to rent and were especially expensive to
operate because of the cost of hiring programmers to perform the complex
operations the computers ran. Such computers were typically found in
large computer centers--operated by industry, government, and private
laboratories--staffed with many programmers and support personnel
(Rogers, 77). By 1956, 76 of IBMÕs large computer mainframes were in
use, compared with only 46 UNIVACÕs (Chposky, 125).
In the 1960s efforts to design and develop the fastest possible
computers with the greatest capacity reached a turning point with the
completion of the LARC machine for Livermore Radiation Laboratories by
the Sperry-Rand Corporation, and the Stretch computer by IBM. The LARC
had a core memory of 98,000 words and multiplied in 10 microseconds.
Stretch was provided with several ranks of memory having slower access
for the ranks of greater capacity, the fastest access time being less
than 1 microseconds and the total capacity in the vicinity of 100
million words (Chposky, 147).
During this time the major computer manufacturers began to offer
a range of computer capabilities, as well as various computer-related
equipment. These included input means such as consoles and card
feeders; output means such as page printers, cathode-ray-tube displays,
and graphing devices; and optional magnetic-tape and magnetic-disk file
storage. These found wide use in business for such applications as
accounting, payroll, inventory control, ordering supplies, and billing.
Central processing units (CPUs) for such purposes did not need to be
very fast arithmetically and were primarily used to access large amounts
of records on file. The greatest number of computer systems were
delivered for the larger applications, such as in hospitals for keeping
track of patient records, medications, and treatments given. They were
also used in automated library systems and in database systems such as
the Chemical Abstracts system, where computer records now on file cover
nearly all known chemical compounds (Rogers, 98).
The trend during the 1970s was, to some extent, away from
extremely powerful, centralized computational centers and toward a
broader range of applications for less-costly computer systems. Most
continuous-process manufacturing, such as petroleum refining and
electrical-power distribution systems, began using computers of
relatively modest capability for controlling and regulating their
activities. In the 1960s the programming of applications problems was
an obstacle to the self-sufficiency of moderate-sized on-site computer
installations, but great advances in applications programming languages
removed these obstacles. Applications languages became available for
controlling a great range of manufacturing processes, for computer
operation of machine tools, and for many other tasks (Osborne, 146). In
1971 Marcian E. Hoff, Jr., an engineer at the Intel Corporation,
invented the microprocessor and another stage in the deveopment of the
computer began (Shallis, 121).
A new revolution in computer hardware was now well under way,
involving miniaturization of computer-logic circuitry and of component
manufacture by what are called large-scale integration techniques. In
the 1950s it was realized that "scaling down" the size of electronic
digital computer circuits and parts would increase speed and efficiency
and improve performance. However, at that time the manufacturing
methods were not good enough to accomplish such a task. About 1960
photoprinting of conductive circuit boards to eliminate wiring became
highly developed. Then it became possible to build resistors and
capacitors into the circuitry by photographic means (Rogers, 142). In
the 1970s entire assemblies, such as adders, shifting registers, and
counters, became available on tiny chips of silicon. In the 1980s very
large scale integration (VLSI), in which hundreds of thousands of
transistors are placed on a single chip, became increasingly common.
Many companies, some new to the computer field, introduced in the 1970s
programmable minicomputers supplied with software packages. The
size-reduction trend continued with the introduction of personal
computers, which are programmable machines small enough and inexpensive
enough to be purchased and used by individuals (Rogers, 153).
One of the first of such machines was introduced in January
1975. Popular Electronics magazine provided plans that would allow any
electronics wizard to build his own small, programmable computer for
about $380 (Rose, 32). The computer was called the ÒAltair 8800Ó. Its
programming involved pushing buttons and flipping switches on the front
of the box. It didnÕt include a monitor or keyboard, and its
applications were very limited (Jacobs, 53). Even though, many orders
came in for it and several famous owners of computer and software
manufacturing companies got their start in computing through the Altair.
For example, Steve Jobs and Steve Wozniak, founders of Apple Computer,
built a much cheaper, yet more productive version of the Altair and
turned their hobby into a business (Fluegelman, 16).
After the introduction of the Altair 8800, the personal computer
industry became a fierce battleground of competition. IBM had been the
computer industry standard for well over a half-century. They held
their position as the standard when they introduced their first personal
computer, the IBM Model 60 in 1975 (Chposky, 156). However, the newly
formed Apple Computer company was releasing its own personal computer,
the Apple II (The Apple I was the first computer designed by Jobs and
Wozniak in WozniakÕs garage, which was not produced on a wide scale).
Software was needed to run the computers as well. Microsoft developed a
Disk Operating System (MS-DOS) for the IBM computer while Apple
developed its own software system (Rose, 37). Because Microsoft had now
set the software standard for IBMs, every software manufacturer had to
make their software compatible with MicrosoftÕs. This would lead to
huge profits for Microsoft (Cringley, 163).
The main goal of the computer manufacturers was to make the
computer as affordable as possible while increasing speed, reliability,
and capacity. Nearly every computer manufacturer accomplished this and
computers popped up everywhere. Computers were in businesses keeping
track of inventories. Computers were in colleges aiding students in
research. Computers were in laboratories making complex calculations at
high speeds for scientists and physicists. The computer had made its
mark everywhere in society and built up a huge industry (Cringley, 174).
The future is promising for the computer industry and its
technology. The speed of processors is expected to double every year
and a half in the coming years. As manufacturing techniques are further
perfected the prices of computer systems are expected to steadily fall.
However, since the microprocessor technology will be increasing, itÕs
higher costs will offset the drop in price of older processors. In other
words, the price of a new computer will stay about the same from year to
year, but technology will steadily increase (Zachary, 42)
Since the end of World War II, the computer industry has grown
from a standing start into one of the biggest and most profitable
industries in the United States. It now comprises thousands of
companies, making everything from multi-million dollar high-speed
supercomputers to printout paper and floppy disks. It employs millions
of people and generates tens of billions of dollars in sales each year
(Malone, 192). Surely, the computer has impacted every aspect of
peopleÕs lives. It has affected the way people work and play. It has
made everyoneÕs life easier by doing difficult work for people. The computer truly is one of the most incredible inventions in history.
Monday, February 11, 2008
3 things to keep ur computer run at max. performance
Although there are many things that can affect the performance of your computer, there are a few simply things you can do each month to help keep your computer running at maximum performance. This article will focus on two problems that impact the performance of your computer and will then explain what you can do about it.
Problem #1: Computer Hard Disk Files
Your computer is always writing information to your hard disk, no matter what you do. Your computer attempts to keep all file information in the same location on your hard drive. As you add and delete files, blank spaces are left between your files. As you add new programs or files, your computer tries to use these blank spaces.
Over time, this reading and writing of files can affect the way your computer performs. The files eventually become scattered in multiple locations on your hard disk rather than in the same location.
Your computer will still find the information. However, the more scattered the information becomes on your hard drive, the more accesses your computer has to make to find (and gather) the information. This requires your hard disk to work harder and do more reading/writing than is necessary. It will slow down your computer by as much as 200% and causes increased wear and tear on your hard drive.
Problem #2: Spyware
If you use the Internet, at some point you will download a file or software program onto your computer. Sometimes you will know something is being downloaded to your computer. Other times you will have no idea. (Although this article will not talk about small files called “cookies”, you may want to look up information on this subject. Cookies are written onto your computer from the Internet.)
Free computer programs (often referred to as Freeware) are a big hit on the Internet. Every day thousands of users download these “free programs”. Although there are some great freeware programs, these programs often have advertisements or tracking code associated with their use. The term “Spyware” refers to programs that gather information about your computer and (Internet) surfing habits without your knowledge. This information is then sold to a third party company as a means of generating revenue.
The problem with Spyware is that it also impacts the performance of your computer. It can make your computer very sluggish and unresponsive.
Three Steps to Improved Computer Performance
Now that we’ve discussed two problems that affect the performance of your computer, let’s discuss three things you can do to get your computer performance back to normal. You should do these three steps in the order presented. Ideally, you should repeat them about once a month or whenever you notice a change in your computer’s performance.
Step #1: Delete Spyware
The first thing you should do is to delete spyware files or programs from your computer. To do this, you can use a free software program such as Ad-Aware SE Personal Edition from LavaSoft. To get the program, go to www.download.com and search for “Ad-Aware SE” (without the quotes). Select “Download Now” and follow the installation instructions. Once the program is installed, you can scan your computer for spyware files. Then, you can select and delete them from your computer.
Note #1: Always be sure to use the “Check for updates now” option to keep your program current.
Note #2: You need to be aware that when you delete spyware files, some of those “free” programs you downloaded may not continue to work correctly. If you have a program you’ve downloaded and want to continue to use, check very carefully what you select to delete from the “Scanning results” once the scan has been completed.
Step #2: Clean up your Hard Disk
Once the spyware is removed, you need to clean up temporary and unwanted files from your hard disk. To do this on your windows PC, select the start option in the lower left hand corner of your computer screen. Then, select the program option. Under the program option, select “Accessories”. Under the “Accessories” option, select “System Tools”. From the System Tools option, select “Disk Cleanup”.
Select the drive you want to clean from the pull-down menu and select OK. Usually, this is Drive C. If you have more than one hard drive, select one at a time. This program will then scan your computer for files that could be erased from your computer. You can safely erase all temporary and Recycle Bin files. You can also check the box of any other files you want the program to erase.
Step #3: Defrag your Hard Disk
Once all the spyware and temporary files are removed, you need to defrag your hard disk. This process simply rewrites your computer files so they are no longer scattered all over your hard disk, but are written in the same location for quick sequential access.
To defrag your hard disk on your windows PC, select the start option in the lower left hand corner of your computer screen. Then, select the program option. Under the program option, select “Accessories”. Under the “Accessories” option, select “System Tools”. From the System Tools option, select “Disk Defragmenter”. First, select the hard drive from your computer. Usually, this is Drive C. However, many computers have multiple hard drives. Select one at a time.
You can select “Analyze” to have the program check out the hard drive and see if it needs to be defragged. The program will prompt you at the completion of its analysis. Use the defragment option as prompted.
Note: If you’ve never used this option before, I would recommend that you select the defragment option.
Once, you’ve completed these three steps, your computer and hard disk should be able to operate at maximum performance. Don’t forget to repeat these steps at least once a month or whenever you notice a change in your computer’s performance.
Problem #1: Computer Hard Disk Files
Your computer is always writing information to your hard disk, no matter what you do. Your computer attempts to keep all file information in the same location on your hard drive. As you add and delete files, blank spaces are left between your files. As you add new programs or files, your computer tries to use these blank spaces.
Over time, this reading and writing of files can affect the way your computer performs. The files eventually become scattered in multiple locations on your hard disk rather than in the same location.
Your computer will still find the information. However, the more scattered the information becomes on your hard drive, the more accesses your computer has to make to find (and gather) the information. This requires your hard disk to work harder and do more reading/writing than is necessary. It will slow down your computer by as much as 200% and causes increased wear and tear on your hard drive.
Problem #2: Spyware
If you use the Internet, at some point you will download a file or software program onto your computer. Sometimes you will know something is being downloaded to your computer. Other times you will have no idea. (Although this article will not talk about small files called “cookies”, you may want to look up information on this subject. Cookies are written onto your computer from the Internet.)
Free computer programs (often referred to as Freeware) are a big hit on the Internet. Every day thousands of users download these “free programs”. Although there are some great freeware programs, these programs often have advertisements or tracking code associated with their use. The term “Spyware” refers to programs that gather information about your computer and (Internet) surfing habits without your knowledge. This information is then sold to a third party company as a means of generating revenue.
The problem with Spyware is that it also impacts the performance of your computer. It can make your computer very sluggish and unresponsive.
Three Steps to Improved Computer Performance
Now that we’ve discussed two problems that affect the performance of your computer, let’s discuss three things you can do to get your computer performance back to normal. You should do these three steps in the order presented. Ideally, you should repeat them about once a month or whenever you notice a change in your computer’s performance.
Step #1: Delete Spyware
The first thing you should do is to delete spyware files or programs from your computer. To do this, you can use a free software program such as Ad-Aware SE Personal Edition from LavaSoft. To get the program, go to www.download.com and search for “Ad-Aware SE” (without the quotes). Select “Download Now” and follow the installation instructions. Once the program is installed, you can scan your computer for spyware files. Then, you can select and delete them from your computer.
Note #1: Always be sure to use the “Check for updates now” option to keep your program current.
Note #2: You need to be aware that when you delete spyware files, some of those “free” programs you downloaded may not continue to work correctly. If you have a program you’ve downloaded and want to continue to use, check very carefully what you select to delete from the “Scanning results” once the scan has been completed.
Step #2: Clean up your Hard Disk
Once the spyware is removed, you need to clean up temporary and unwanted files from your hard disk. To do this on your windows PC, select the start option in the lower left hand corner of your computer screen. Then, select the program option. Under the program option, select “Accessories”. Under the “Accessories” option, select “System Tools”. From the System Tools option, select “Disk Cleanup”.
Select the drive you want to clean from the pull-down menu and select OK. Usually, this is Drive C. If you have more than one hard drive, select one at a time. This program will then scan your computer for files that could be erased from your computer. You can safely erase all temporary and Recycle Bin files. You can also check the box of any other files you want the program to erase.
Step #3: Defrag your Hard Disk
Once all the spyware and temporary files are removed, you need to defrag your hard disk. This process simply rewrites your computer files so they are no longer scattered all over your hard disk, but are written in the same location for quick sequential access.
To defrag your hard disk on your windows PC, select the start option in the lower left hand corner of your computer screen. Then, select the program option. Under the program option, select “Accessories”. Under the “Accessories” option, select “System Tools”. From the System Tools option, select “Disk Defragmenter”. First, select the hard drive from your computer. Usually, this is Drive C. However, many computers have multiple hard drives. Select one at a time.
You can select “Analyze” to have the program check out the hard drive and see if it needs to be defragged. The program will prompt you at the completion of its analysis. Use the defragment option as prompted.
Note: If you’ve never used this option before, I would recommend that you select the defragment option.
Once, you’ve completed these three steps, your computer and hard disk should be able to operate at maximum performance. Don’t forget to repeat these steps at least once a month or whenever you notice a change in your computer’s performance.
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