GLOSSARY OF TERMS

INDEX:     A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Analog Line - Voice grade telecommunications line used for  telephones.  A computer communicates over an analog line through a modem at each end of the connection.  The modems convert digital information to analog, then back to digital.

 Anti-virus Software - A utility program that detects and eliminates computer viruses.

Apple Talk - A network protocol capable of transferring data at a rate of up to 230 kilobits per second over shielded twisted pair wire.  Used to  connect Apple type computers and peripherials.

Applet - A small Java program that can be embedded in an HTML Web page.

ASCII - American Standard Code for Information Interchange - The world wide standard code of 0s and 1s used to  represent all letters, numbers, and other symbols used by computers.  There are 128 standard ASCII codes each of which can be represented by a 7 digit binary number: 0000000 through 1111111.

 Asynchronous Transmission - Data transmission method that uses start and stop bits to coordinate the flow of data. 

ATM - Asynchronous Transfer Mode.

Backbone - The portion of the network that carries the bulk of the traffic.

Bad  Sector - An area on a hard disk or floppy disk that can not be used to store data due to a manufacturing defect or accidental damage.  The operating system will find and isolate the bad sectors so that they are not used to store data.

 Bandwidth - The range of transmission frequencies that a network can use.  The greater ther bandwidth, the greater the amount of data that a cable can carry.  Bandwith is measured in bits per second (bps) for digital signals, or in  herts (Hz) for analog signals.

Baud Rate - Usually refers to the data transfer rate of a modem and measured in bits/second.

BIOS - Basic Input/Output System.  It is a set of instructions stored in a read-only memory (ROM) chip on the  computer's main circuit board that allows the computer's hardware and operating system to cummunicate with application programs and peripheral devices.

Bit - The smallest unit of computerized data - a 1 or 0 binary digit.

 BPS - Bits Per Second - A measure of how fast data is moving.  A 28.8K modem transfers data at 28,800 bits per second.

Browser - An application used to retrieve and display HTML documents.

 Byte - A set of bits that represent a single character.  Usually there are 8 bits in a byte.   

Cache - A special area of memory managed by a cache controller, that stores the contents of frequently accessed memory  locations and their addresses.  The greater the cache memory, the faster the system performance.

CAD - Computer Aided Design.

 CD-R - Compact Disc-Recordable - A recordable CD-ROM technology that uses a disc that can be written only once. 

CD-ROM - Compact Disc-Read Only Memory - A high capacity, optical storage technology that uses a compact disc to store  large amounts of information.  Conventional CD-ROMS hold up to 650 MB of data or approximately 250,000 pages of text.

CD-RW - Compact Disc-Rewritable - CD-ROM technology that uses a disc that can be written to many times.

CGI - Common  Gateway Interface - An interface for running external programs or scripts under an information server, such as a Web server.  One common use of a CGI script is to handle data from HTML forms.  Usually a CGI program is a small program  that takes data from a web server and does something with it, like putting the content of a form into an e-mail message.

Client - A software program that is used to contact and ovtain data from a different computer such as a file  server.  Each client program is designed to work with one or more specific kinds of server programs, and each server requires a specific kind of client. 

 Client/server Architecture - A computing architecture that distributes processing between clients and servers on a network.

Cookie - Information sent by a Web server to a Web browser and then sent back to the Web server.  Cookies might  contain information such as login or registration information.

CRT - Cathode Ray Tube

DAT - Digital Audio Tape

Data Compression - Any method of encoding data so that it occupies less space than its original form.

 DDE - Dynamic Data Exchange.

DIMM - Dual Inline Memory Module.

Disk Cache - An area of computer memory where data is temporarily stored on its way to or from a disk drive.  A disk cache program can significantly speed up most disk  operations.

Disk Duplexing -A fault tolerant technique that writes the same information simultaneously onto two hard disk drives, with the same information simultaneously onto two hard disk drives, with each drive having its own controller.

 Disk Mirroring - A fault tolerant technique that writes the same information simultaneously onto two hard disk drives, using a singel controller.

Disk Optimizer - A utility program that rearranges files and directories on a disk for optimum  performance.  A disk optimizer will rewrite fragmented files as contiguous files.

DLL - Dynamic Link Library.

DMA - Direct Memory Access.

DOS - Disk Operating System.

Dot Pitch - A measurement of distance between the centers of  two same-color phosphor dots on the screen.  The closer the dots, the smaller the dot pitch, and the sharper the image.

DRAM - Dynamic Random Access Memory.

DSL - Digital Subscriver Line - A method of moving data over regular  telephone lines.  A DSL connection will allow much faster data transfer rates than a standard modem.

DTR - Data Terminal Ready.

DVD - Digital Video Disc or Digital Versatile Disc - An optical storage technology that holds 4.7 GB of  data on a single layer, single-sided disc, enough for a movie.  Future versions of DVD will have additional capacity by using two layers and two sides.

ECC - Error Correction Code.

EDO - Extended Data Out.

 EEPROM - Electrically Erasable Programmable Read-Only Memory.

Encryption - A coding technique used to secure sensitive data.

EPROM - Erasable Programmable Read-Only Memory.

Ethernet - A popular network protocol and cabling  scheme.   Ethernet uses a bus topology capable of connecting up to 1024 devices within each main branch

Expansion Bus - An extension of the main computer bus that includes expansion slots for adding compatible adapters such as  video cards, modems, etc.

FDDI - Fiver Distributed Data Interface - A specification for fiver-optic networks transmitting at a speed of up to 100 megavits per second over a dual, counter-rotating, token-ring topology.

 File Server - A networked computer used to store files for access byh other client computers.

Fire Wall - A combination of software and hardware that separates a LAN into two or more parts for security purposes. 

 FTP - File Transfer Protocol - A method of transferring one or more files from one computer to another, often over a modem.

Gateway - A device for interconnecting two or more dissimilar networks.

 GIF - Fraphics Interchange Format - This is a raster graphics file format that handles 8-bit color (256 colors).

GUI - Graphical User Interface - An interface that allows users to interact with the computer by pointing to pictorial  representations on the screen rather than by typing command at a command prompt.

Handshaking - The exchange of control codes or particular characters to maintain and coordiante data flow between two devices, so that data is only transmitted  when the teceiving device is ready to accept the data.

Hardware Interrupt - A request for serice generated by a hardware device such as a keyboard, mouse or printer.  Since the processor may receive several requests at the same time,  hardware interrupts are usually assigned a priority level.

Hayes Compatible Modem - Any modem that supports the commands in the industry standard ATcommand set, definded by Hayes Microcomputer Products.

 HTML - Hypertext Markup Language - The language used to create Web pages.

HTTP - HyperText Transfer Protocol - The protocol used to transfer HTML documents on the Web.

HUB - The central controlling device in a star network.

 Hyperlink - The underlined or emphasized word or phrase on a Web page that, when selected, displays another document.

Hypertext - A document that contains links to other parts of the document or to other documents. 

I/O - Input.Output

IC - Integrated Circuit.

IDE - Integrated Drive Electronics - A popular hard disk interface standard.  IDE gets its name from the fact that the electronic control circuitry needed is located on the drive itself, eliminating the need  for a separate hard disk controller card.

Internet - A set of computer networks consisting of a large number of smaller networks, using different networking protocols.

Intranet - A private network inside a company or organization that uses  the same kind of software that you would find on the public Internet, but is for internal use.

IP Address - A unique number consisting of four parts separated by dots.  Every machine that is on the Internet has a unique IP number.

 ISP - Internet Service Provider - A company\ that provides Internet accounts and access to the Internet.

IRQ - Interrupt Request.

ISA - Industry Standard Architecture - The 16 bit bus design first used in the IBM PC/AT computer.

ISDN -  Integrated Services Digital Network - A worldwide digital communications netwrok capable of transmitting voice, video, music, and data.  Provides 144 Kbps over a single phone line (divided into two 64 Kbps "B" channels and one 16 Kbps "D"  channel).

Java - A programmng language invented by Sun Microsystems that is specifically designed for writing programs that can be safely downloaded to your computer through the Internet and immediately run without fear of viruses or other  harm to you computer or files. 

JPEG - Joint Photographic Experts Group - An ISO/ITU-TSS standard for compressing still images such as photographs, single video frames, or scanned pictures.  Two main reasons for using JPEG are to  reduce the amount of disk space an image occupies and to store 24-bit per pixel color data.  GIF, the other popular format used on the Web and in multimedia, can only store 8 bits per pixel (256 or fewer colors).  JPEG images look  much better than GIFs on hardware that can handle more than 256 colors.

Kbps - Kilobits per second.

LAN - Local Area Network - A group of computers and associated peripherals connected by a communications channel capable of sharing files  and other resources between multiple users.

Leased Line - A communications circuit or telephone line reserved for the permanent use of a specific customer.

Mbps - Megabits per second.

Megabyte - A million bytes or 1024 kilobytes.

 Memory - The primary random access memory (RAM) installed in a computer.  The amount of memory installed in the computer dictactes the size and number of programs that it can run.

MHz - HegaHetz.

 MIDI - Musical Instrument Device Interface.

MIME - Multipurpose Internet Mail Extensions - The standar for attaching non-text files to standard internet mail messages. 

 MIPS - Million of Instructions Per Second - A measure of the processing speed of a computer's central processing unit.

MPEG - Motion Picture Experts Group - An ISO/ITU-TSS standard for compuressing full-motion video.  MPEG takes  advantage of the fact that full- motion is made up of many successive frames consisting of large areas that are unchanged.  If parts of the image have not changed, MPEG notes and stores this information.

MTBF - Mean Time Between Failure.

Multiplexer - A device that merges several lower-speed transmission channels into one high speed channel at one end of the link.  A multiplexer at the other end of the link reverses the process to reproduce the low speed channels.

 Multiprocessing - The ability of an operating system to use more than one CPU in a singel comuter.  Symmetriacal multiprocessing refers to the operating system's avility to assign tasks dynamically to the nest available processor. 

 Multitasking - The simultaneous execution of two or more programs in one computer.

NIC - Network Interface Card - The board that plugs into a computer or server and works with the network operating system to control the flow of information  over the network.

Nonvolatile Memory - Any form of memory that retains its contents when power is removed.  ROM, EPROM, and EEPROM are forms of nonvolatile memory.

 NTSC - National Television System Committee - A group founded to establish broadcast television standards in North America.

NuBus - The 32 bit bus used in the Mac II and later computers to accept expansion cards.

 OCR - Optical Character Recognition.

OEM - Original Equipment Manufacturer.

OLE - Object Linking adn Embedding - A protocol for application-to-application communications.  OLE gives application programs a two way updaing capability.

 Parallel Processing - The simultaneous processing of different tasks in a program by two or more microprocessors.  Parallel processing can be carried out by a single computer with more than one CPU, or by several computers connected  together in a network.

Parity - A simple form of error checking that uses an extra, or fedundant bit.  Parity may be set to even, odd, mark, space, or none.

 Partition - A section of a hard disk that functions as an independent hard disk.

PCMCIA - Personal Computer Memory Card International Association - A PCMCIA card is a credit card size plug in adapter aimed at mobile computers.  The  PCMCIA devices include modems, network adapters, dynamic RAM, flash memory cards, mini-hard disks, and SCSI adapters.

Plug and Play - An architechture for personal computers characterized by the computer's ability to identify an added  component and configure itself with respect to this component.

POP - Point of Presence / Post Office Protocol - Point of presence usually means a location where internet users receive local connection capabilities to the internet.  Post  office protocol refers to the way email software gets mail from a mail server. 

PPP - Point to Point Protocol.

RAID - Redundant Array of Inexpensive Disks - A group of disk drives over which data is distributed, to facilitate faster  storage, faster retieval, and greater data security than would be possible with a single disk drive.

RAM - Random Access Memory.

Refresh Rate - Measures the speed that the entire screen is rescanned.  Higher frequencies reduce  flicker, because they light the pixels more frequently, reducing the dimming that causes flicker; also called vertical frequency.

Resolution - The clarity or fineness of detail that can be distinguished in an image, especially one produced  by a monitor (measured in pixels) or printer (measured in dots per inch).

RISC - Reduced Instruction Set Computer - A design that restricts the number of instructions that a microprocessor can handle.  RISC architecture speeds up  processing by eliminating the least used instructions.

ROM - Read Only Memory.

Router - A device in a network that handles message transfer between computers.  A router receives information and forwards it based on what the router  determines to be the most efficient route at the time of transmission

SCSI - Small Computer Systems Interface - A standard parallel interface for rapid data transmission, capable of supporting as many as seven devices per SCSI port.

 SDLC - Synchronous Data Link Control.

Search Engine - A program on the Web that finds information on a given topic.

Security Certificate - Information used by the SSL protocol to establish a secure connection.  Security certificates  contain information about who it belongs to, who it was issued by, a unique serial number or other unique identification used to verify the contents of the certificate.

SLIP - Serial Line Internet Protocol - A standard for usin a regular  telephone line and a modem to connect a computer as a real Internet site.  SLIP is gradually being replaced by PPP.

 SMTP - Simple Network Management Protocol - A set of standards for communication with devices connected to a TCP/IP network. 

Sound Card - An expansion card that enables digitally reproduces a wide range of sounds.

 SQL - Structured Query Language.

SRAM - Static RAM - A type of random access memory that does not need to be refreshed as often as dynamic RAM.  Faster than dynamic RAM and often used for cache memory.

 SSL - Secure Sockets Layer - A protocol designed by Netscape to enabel encrypted, authenticated communications across the Internet.

Striping - Used with disk arrays in file servers.  A technique for improving disk storage and  retrieval.  Each file written onto a disk array is spread, or striped, over several drives.

TCP/IP - Transfer Control Protocol/Internet Protocol - A group of protocols for network communications routing and data transfer.  TCP/IP  is the accepted standard for UNIX based operating systems and for the Internet.

TIFF - Tagged Image File Format.

UART - Universal Asynchronous Receiver/Transmitter.

UMB - Upper Memory Block.

 UNIX - A trademark for an interactive multiuser, time sharing operating system originally invented at AT&T Bell Labs.

UPS - Uniterruptible Power Supply.

 URL - Uniform Resource Locator - An address that identifies the locations of every page, graphic image, and file on the Web.

VGA - Video Graphics Arry - A graphics display system developed by IBM. 

Virtual Memory - A memory  management technique that allows information to be swapped out to a hard disk, providing applications with more memory space than is actually available in the computer.

 Virus - A program intended to damage or interfere with your computer system without your knowledge or permission.

VPN - Virtual Private Network - A netwok in which some of the parts are connected using the public Internet, but the data sent  across the Internet is encrypted, so the entire network is private.

VRAM - Video Random Access Memory - A form of dynamic RAM for visual data that is located on the video adapter or system board. 

 WAN - Wide Area Network - Any network that covers an area larger than a single building or campus.

WYSIWYG - What You See Is What You Get.