WAN (Wide Area Network)

A network that spans a large geographical area. The network is connected by means of telephone lines, ISDN (Integrated Services Digital Network) lines, DSL, cable, radio waves, or satellite links.

Define Volts

The unit of electromotive force, or the potential energy, that will produce a current of 1 ampere when steadily applied against a resistance of 1 ohm. Voltage is also considered the potential energy of a circuit.

Virtual Memory

Hard disk space that can be used as additional memory for holding data not immediately required by the processor.

Virtual Control Program Interface (VCPI)

A memory management specification that accesses extended memory for MS-DOS-based applications. It allows only one application to control extended memory and does not support multi-tasking. Windows is not compatible with the VCPI specification.

VGA (Video Graphics Array)

A graphics adapter that offers 16 colors at a resolution of 640 pixels × 480 pixels. To gain more colors, VGA uses an analog video signal instead of a digital signal. With the analog signal, the VGA standard is able to provide 64 distinct levels for each color, giving users 643 or 262,144 possible colors. It uses a 15-pin, three-row, female DB-type connector.

Vertical Refresh Rate (VRR)

The speed at which a monitor completes all vertical traces.


The vast collection of discussion groups and newsgroups on the Internet.

USB (Universal Serial Bus)

A new external expansion bus that is popular for use with low-speed mass storage devices such as Zip drives, modems, and printers.

UPS (Uninterruptible Power Supply)

Acts as both a surge suppressor and a power leveler to provide the computer with a constant source of power. It also provides power during a power failure or interruption so the user can safely save data before shutting down.


The ability to transfer (send) a file from one computer to a remote computer.

UMB (upper memory block)

Unused spaces in upper memory that can be divided into blocks. These empty blocks have no RAM associated with them and are simply reserved space. This unused space is valuable because, unlike expanded and extended memory, MS-DOS can run programs in UMB.

UMA (Upper Memory Area)

The area from 640 KB to 1024 KB that is designated for hardware needs such as video RAM, BIOS, and memory-mapped hardware.

Twisted-pair Cable

Consists of two insulated wires twisted around each other to form a pair. One or more twisted pairs are used in a twisted-pair cable.

TSR (terminate-and-stay-resident program)

A computer program, also known as a memory-resident program, that remains in memory after being run so that it can be called up later. These extend the capabilities of the operating system or provide "pop-up" functions (such as a calendar or calculator) that can be brought up in the middle of another program without disturbing that program. These programs were popular in the days of MS-DOS, but lead to numerous problems due to memory usage conflicts.


An electronic device that allows a small current in one place to control a larger current in another place; commonly used as amplifiers in radio and audio circuits.


The layout scheme that describes the way in which network nodes are wired in relation to each other.

Define Telnet

A terminal emulation program that allows you to log on to another computer system over the Internet. You can then run programs on that machine as though you dialed in directly.


The ability to transmit data over telephone lines to a remote computer.

Telecom Software

An application that allows two computers to communicate. Both computers must use compatible software for communication to take place.

TCP/IP (Transfer Control Protocol/Internet Protocol)

The name given to a collection of protocols that were designed in the 1970s for use on the large-scale mixed platform that became the Internet.

Tape Drive

A high-capacity removable magnetic data storage device ideal for backups and retrieval of large amounts of data. Works like a tape recorder and saves information in a linear format.

System Crystal

Determines the speed at which a CPU (central processing unit) is operated (sets the clock speed); it is usually a quartz oscillator.

System Bus

Supports the CPU (central processing unit), RAM (random access memory), and other motherboard components that provide the controlling element to the computer. It is responsible for coordinating the operation of the individual system components and central to the communications system of a computer. Also called the control bus.

Sysop (System Operator)

The system operator of a small BBS (bulletin board system). (Pronounced "SIS-op.")


Specific rules that prescribe how the symbols of a programming language can be written to form meaningful statements that will be understood by the PC.


Form of computer communication in which data is transmitted in packets containing more than one character. This is faster than asynchronous transmission because there is no start/stop bit between each individual character.

Switch Box

Allows the user to manually (or automatically) switch cable connections so that one computer can use several different printers or devices with one parallel port.

SVGA (Super Video Graphics Array)

A video standard. The minimum requirement for SVGA compatibility is 640 pixels × 480 pixels at 256 colors. At the low end, typical SVGA systems are operated at 800 × 600 at any color depth. Today, most SVGAs run at 1024 × 768 at 256 with 64 K colors or better.

Surge Suppressor

Used to prevent large power spikes (such as from lightning) from damaging a computer.


Technology found in Pentium processors allowing the Pentium to have two instruction pipelines, thereby increasing the speed of processing.

Star Network

A type of network configuration in which all computers are connected to a central point called a hub. The hub collects and distributes the flow data within the network. In large networks, several hubs may be connected. This is the easiest form of network topology to troubleshoot because all information goes through a hub, making it easier to isolate problems.


Holds computer output before sending it to a printer. This enables the main program to run more quickly because the print spooler handles output. The print spooler then distributes output to the printer at the proper speed.


Any program (set of instructions) that causes a computer to carry out a task or function.

Shadow RAM

Many high-speed motherboards use shadow RAM to improve the performance of a computer. Shadow RAM rewrites (or shadows) the contents of the ROM BIOS and/or video BIOS into extended RAM (between the 640-KB boundary and 1 MB). This allows systems to operate faster when application software calls BIOS routines. In some cases, system speed can be increased up to 400 percent.

Server Network

This type of network requires a central server (dedicated computer) to manage access to all shared files and peripherals.


The computer that runs the network operating system, manages security, and administers access to resources; strictly speaking, any computer that stores information and allows outside users to get copies of that information.


Transmission of one bit at a time over a single wire.

Search Engine

A program that searches indexes of Internet addresses using keywords. There are hundreds of search engines located on servers throughout the Internet. Popular search engines include Google, AltaVista, Bing, Yahoo, HotBot, and Excite.

SCSI (Small Computer System Interface)

A standard way of interfacing a computer to disk drives and other devices that require high-speed data transfer. Up to 16 SCSI devices, including the host adapter, can be connected in a daisy chain fashion. These devices can be hard disk drives, CD-ROMs, scanners, or printers. SCSI is the only common computer interface that allows adding both internal and external devices on the same chain. (Pronounced "scuzzy.")


A process that converts a photograph, graphic, or text image found on paper into an electronic computer file.


A peripheral that converts information from the written page (or a printed graphic) to digital information that can be used by the computer. Works in a manner similar to the scanning process in a photocopy machine.


A device that works like a bridge but is able to select the best route from network to network based on traffic load. A router can also connect dissimilar networks.

ROM (Read-Only Memory)

Computer memory that contains instructions that do not need to be changed, such as operating system startup instructions. The computer can access data from ROM but cannot put new data into it.

RISC (Reduced Instruction Set Computing)

Uses a smaller and simpler set of instructions to control the processor, thereby greatly enhancing the processing speed.

Ring Network

A type of network in which all the servers and clients are connected in a closed loop.


A measurement of the detail of images produced by a monitor or printer. Normally measured by a horizontal and vertical number of pixels for monitors or dpi (dots per inch) for laser printers. The higher the number, the better the quality and the more memory required by the system.


A device that works like an amplifier; it increases or boosts a signal to allow transmissions over longer distances.


A file or set of files in Microsoft Windows 95 and later versions that stores information about a computer's hardware and software configuration.


Temporary memory storage areas located inside the CPU (central processing unit). Used to hold the intermediate results of calculations or other operations.

Real Mode

An MS-DOS mode in which a computer can perform only one operation at a time and an application expects full control of the system. Real mode operates within the MS-DOS 1-MB limitation.

RAM (Random Access Memory)

The main memory where a computer temporarily stores data.

RAID (Redundant Array of Independent Disks)

The combining of several drives using either hardware or software controls to make them seem to be one drive.