Protected Mode

A mode introduced with 80286 processors that used an operating system like OS/2 or Windows to allow creation of virtual machines. These provided the functionality of a standard computer in real mode but allowed multiple tasks to take place at the same time. The term refers to the fact that processor, memory, and other hardware are "protected" from the software applications by the operating system, which allocates the memory and processor time.


A set of rules that govern the transfer of information. The format used to upload or download files to allow two different computers to communicate in a standard format.

Define Prompt

The command prompt—a user interface provided by COMMAND.COM in MS-DOS to signal to the user that the computer is ready to receive input (for example, C:\> or A:\>).

Professional Graphics Adapter (PGA)

An adapter that was originally marketed to the engineering and scientific communities. It was expensive and required three ISA (Industry Standard Architecture) slots when fully configured. This system offered 3-D rotation and 60 frames per second animation. It used a 15-pin, three-row, female DB-type connector. It gained limited use in CAD environments, but was quickly replaced by better mass-market solutions.


A peripheral device that transfers computer output to paper or other form of hard copy.

Power Supply

Takes alternating current (AC) power from a local source (a wall outlet) and converts it to direct current (DC) for on-board electronics use.

Define Power

The strength or force actually put forth by electricity. Electrical power is measured in watts, which is measured by multiplying voltage by current.


Specific channel used by a network service. For example, Gopher often uses port 70, while some Web sites use port 80.


Similar to a printer, but uses pens to draw an image. Used most often with graphics and drawing programs.


Short for "picture element." One of the dots that make up a graphical image.


The amount of time a pixel stays visible on a monitor screen, which is a factor of the decay of activity in the phosphor coating.


An external device connected to a computer such as a printer, scanner, modem, or joystick.

Peer-to-Peer Network

A network in which each connected computer acts as either a server or a client depending on the users' needs. Each user or workstation establishes its own security and determines which resources are available to other users. These networks are limited in size, usually no more than 15 to 20 workstations.


The address to a file. The path consists of the drive name, the location of the file in the directory structure, and the filename. Example: C:\Mystuff\MYFILE.DOC.

Parity Bit

A very basic type of error-correcting code that uses the value of an extra bit sent at the end of a data string. The bit must have a set value based on an algorithm to verify that the data at the receiving end is correct.

Define Parallel

The transmission of several bits at the same time over separate wires.

Define Packet

A group of consecutive characters transmitted from one computer to another over a network.

Operating System

The program that controls a PC and makes it possible for users to run their own applications. The operating system provides the built-in routines that allow the computer to recognize commands, manage files, connect devices, and perform I/O (input/output) operations.

Define Online

The state in which two or more computers are connected to each other, making data transmission possible.

ohm Ω

A unit of electrical resistance.

Offline Reader

A program to display e-mail messages that have been downloaded to a computer.

Define Offline

Networked computers that are not actively connected so that transmission of data is not possible.

NetBIOS/NetBEUI (networked basic input/output system/NetBios Enhanced User Interface)

A local area networking protocol developed by IBM and refined by Microsoft; originally, the native protocol for LAN Manager and Windows NT. IBM developed NetBIOS as a way to permit small groups of computers to share files and printers efficiently. NetBIOS is the original edition; NetBEUI is an enhanced version for more powerful networks in the 32-bit operating system.

Network Card

An expansion card that connects a computer to a group of computers so they can access information and programs. Also known as a network interface card (NIC) and network adapter card.

Define Network

A group of computers connected together to share data and resources.

Nanosecond (ns)

One-billionth of one second. The time increment used to measure access speed of the memory chip.


The operation of more than one application at what appears to be the same time on the same PC. The CPU (central processing unit) quickly switches between the various programs, making it possible to work in more than one program at once.

MTBF (Mean Time Between Failures)

A standard means by which vendors estimate the expected life span of a given product line.


Device used with graphical environments to point and select objects on the system's monitor. They come in a variety of shapes and sizes.


Also known as a PWB or printed wiring board, it is the large circuit board found inside the computer. For all practical purposes, it is the computer. It contains the following items: chip set, data bus, address bus, expansion slots, clock, battery, and memory.


The primary output device, which resembles a television set. It visually displays text and graphics.

Molex Connector

Type of power supply connector primarily used for devices that need both 12-volt and 5-volt power (floppy disk drives). The most common type of connector.

Modem (MOdulator/DEModulator)

Converts computer data to information that can be transmitted via wires (telephone, ISDN, fiber optics) and wireless communication. Allows communication between computers over long and short distances.


A type of power supply connector primarily used on 3.5-inch floppy disk drives.

Microsoft Control Panel

The new interface for system management tools that was introduced with Microsoft Windows NT. It offers a single interface to access and utilize a variety of tools.


An integrated circuit containing the entire CPU (central processing unit) of a computer, all on one chip, so that only the memory and I/O (input/output) devices need to be added.


Just like the microphone on a tape recorder. Allows input of voice or music to be recorded and saved to a computer file.

Micro Channel Architecture (MCA)

A short-lived, 32-bit expansion bus that was a proprietary design of IBM used on the IBM PS/2 computer. By abandoning the open design of the existing PC market, IBM limited the willingness of developers and buyers alike to use MCA.

Define Memory

The area within a computer where information is stored while being worked on. It stores information (in the form of data bits) that the CPU (central processing unit) and software need to keep running.

Megahertz (MHz)

One million hertz (one million cycles per second). A measurement of CPU clock speed.

MegaByte (MB)

An amount of computer memory equal to 220. 1,048,576 bytes = 1024 kilobytes. One megabyte can store more than one million characters.

MDA (Monochrome Display Adapter)

Displays text only at a resolution of 720 pixels × 350 pixels. An MDA is perfect for use with MS-DOS-based word-processing and spreadsheet programs. The MDA uses a 9-pin male connector.

Mailing List

A list of subscribers to a particular discussion group. This database can also be used to distribute e-zines (electronic magazines).


The names assigned to the parallel printer ports on a PC.

Logging On

Means by which—when connecting to a remote computer—the host computer (the one that is called) gives permission to connect. The process of sending the appropriate information to sign on is called logging on. Often a user name and password are required.

Local Bus

A separate bus in the computer designed to provide extra-fast access to the CPU (central processing unit) for certain devices, such as video cards.

Link aka Hyperlink

Link Means, also known as a hyperlink, by which a reader is moved to a different location on the Internet when the link is activated. When text is used for a hyperlink, it is often colored differently from the body text of the page so it stands out.

LAN (Local Area Network)

A network that covers a limited distance (such as a single building or facility) to allow computers to share information and resources.

Kilobyte (KB)

A unit of memory equal to 1024 characters or bytes (1 KB = one kilobyte).

Define Keyboard

A primary input device much like a typewriter, used for entering text and command function shortcuts into a computer.

Internet Service Provider (ISP)

A host computer that users can dial into over a modem to connect to the Internet.

International Organization for Standardization (ISO)

Groups of experts drawn from the industry that set standards for various technologies. The work of these teams has led to development of SCSI (Small Computer System Interface), SGML and Internet standards, as well as the ASCII character set.


A telecommunication standard that allows a channel to carry voice and data in digital form over a single line.

ISA (Industry Standard Architecture)

One of several common expansion slot and card designs.

IRQ (Interrupt Request)

A wire used by the CPU (central processing unit) to control the flow of data. It prevents devices from trying to communicate with the CPU at the same time by "interrupting" and temporarily stopping the CPU to deal with a particular request.

IPX/SPX (Internetwork Packet Exchange/ Sequenced Packet Exchange)

NetWare core protocol developed by Novell in the early 1980s.

IP address (Internet Protocol address)

A unique address that identifies every network and host on the Internet. (A host is defined as the TCP/IP network interface within the computer, not the computer itself—a computer with two network cards will have two IP addresses.)

IP (Internet Protocol)

The protocol used to define how data is transmitted over the Internet.

I/O Address

A unique name assigned to each device that allows the CPU (central processing unit) to recognize the device with which it is communicating.


A system that links computer networks all over the world.

internal cache

High-speed memory built into the processor to store frequently used data. This bypasses the need to access slower devices such as RAM (random access memory) or hard drives.

Integrated Circuit (IC)

An electronic device consisting of many miniature transistors and other circuit elements (resistors, capacitors, and so forth).

IDE (Integrated Device Electronics)

The most common standard for interfacing hard disk and CD-ROM drives in the PC environment. Much of the actual work of controlling the hard disk drive is handled by the system BIOS. This reduces hardware cost but introduces an overall system performance penalty during I/O (input/output) operations. See also Enhanced IDE (EIDE).

Define icon - What is icon

A small picture on a computer screen used in Windows (or other graphical operating system) to represent a group of files, an object, or operations. A user accesses the item he or she wants by clicking on the picture with the mouse.

HTTP (Hypertext Transfer Protocol)

The protocol used to transmit data in the HTML (Hypertext Markup Langage) format.

HTML (Hypertext Markup Language)

An application of SGML (Standardized General Markup Language) used to create Web pages.

Horizontal Refresh Rate (HRR)

The speed at which the electron beam in a CRT completes one horizontal trace.

Define Gopher - What is Gopher

A system of information retrieval that "digs" down through layers of menus to reach what you want. A Gopher system is generally text-based and is best for finding documents buried in archives such as university libraries. Some Web sites offer access to Gopher, but it has largely been replaced by information archives on Web sites.

General Protection Fault (GPF)

An error that occurs in Microsoft Windows when a program tries to access a memory location that is not allocated to it.

Define Gateway - What is Gateway

A link between different computer networks. It is usually a computer that acts as a translator between two completely dissimilar systems. Because it is both a translator and a router, it is usually slower than a bridge or router alone.


Scattering of data in files throughout a disk drive caused by the continual addition and deletion of files. Although not harmful to the computer, fragmentation slows down a hard drive because it causes the computer to access two or more places to retrieve a file. (You can alleviate this problem by running a defragmentation program.)

Form Factor

The standard physical configuration of a typical device such as a motherboard or a 3.5-inch hard disk drive.

Floppy Disk Drive

Low-capacity magnetic removable storage drive.

File Transfer Protocol (FTP)

(1) An application used for transferring files to and from another computer, usually over the Internet.

(2) The protocol by means of which these transfers take place.

Filenames (Filespec)

Ways to designate files. A traditional DOS filename is made up of three parts—a name of up to eight characters, a period, and an extension of up to three characters. The name can include any number, character, or the following symbols: _()~'!%$&#. For example: MYFILE.DOC. Spaces cannot be used in MS-DOS filenames. Long filenames used in newer operating systems can be much longer and include spaces.

Fiber-Optic Cable

A cable that is made out of light-conducting glass or plastic fibers. Multiple fiber cores can be bundled in the center of its protective tubing.

Expansion Slots

Specialized sockets that allow additional devices (circuit boards/adapter cards) to be attached to the motherboard (by means of the expansion bus). These are used to expand or customize a computer. They are an extension of the computer's bus system.

Expansion Buses

Provide the connection between expansion cards (drive controllers, video cards, modems, and so forth) and the system bus.

Define Ethernet - What is Ethernet

A type of local area network in which communication takes place by means of radio frequency signals carried by a coaxial cable.

Error Messages

Brief technical messages that are displayed by an application or operating system when an error occurs.

Enhanced Parallel Port (EPP)

Features 2 MB per second data transfer rates, bidirectional 8-bit operation, and addressing to support multiple (daisy-chained) peripherals on a single computer.

Enhanced IDE (EIDE)

A standard developed to increase the size of available disk drives and the speed of data transfer between the host and the disk drive.

Expanded Memory Specification (EMS)

A technique, developed by Lotus/Intel/Microsoft (LIM), that adds addressable memory to a computer system, overcoming the original MS-DOS upper memory limit. The LIM EMS uses a 64-KB section of memory (usually in upper memory) to provide a "window" into which data can be written. Once in this area, the data can be transferred to the expanded memory. The memory chips are located on an expansion card installed inside the computer.

E-mail (Electronic Mail)

The transmission of messages by computer from one person to another, often via the Internet.

Enhanced Graphics Adapter (EGA)

An improvement on the older CGA standard. Supports a resolution of up to 640 pixels × 350 pixels at 16 colors in text-only mode or 640 × 200 at 2 colors in graphics mode. The EGA standard was not fully backward-compatible with CGA and MDA (Monochrome Display Adapter).

Enhanced Capabilities Port (ECP)

Developed by Hewlett-Packard and Microsoft. It features 2 MB per second data transfer and bidirectional 8-bit operation. ECP specifies whether transmitted information consists of data or commands for the peripheral.

Error-Correction Coding (ECC)

The use of a code to verify or disprove that a data string received is the same as the data sent.

Dynamic Random Access Memory (DRAM)

Memory that requires a refresh signal to be sent to it periodically.