common computer, A+ glossary, computer A plus terms
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Commonly used computer and A+ glossary

In this section, we provide you with the glossary of commonly used computer terms. You can use these terms to learn computer or used as a reference for your learning. And best of all, these terms are the terms used in A+ examination. Since there are lots of them, you can use "ctrl+f" keys to search for the terms you want to know.

386 enhanced mode: The most advanced and complex of the different operating modes in the early Microsoft Windows 3.x is 386 enhanced mode. It lets Windows access the protected mode of the 80386 (or higher) processor for extended memory management and multitasking for both Windows and non-Windows application programs.

802.3: It is a LAN technology with some WAN applications and collection of IEEE standards defining the Physical Layer and Data Link Layer's media access control (MAC) sublayer of wired Ethernet. Physical connections are made between nodes and/or infrastructure devices (hubs, switches, routers) by various types of copper or fiber cable. 802.3 is a technology that supports the IEEE 802.1 network architecture.

802.5: An IEEE standard for a token ring local area network access method and it is implemented in Token Ring.

8086: The 8086 is a 16-bit microprocessor chip designed by Intel and introduced to the market in 1978, which gave rise to the x86 architecture. The Intel 8088, released in 1979, was a slightly modified chip with an external 8-bit data bus allowing the use of cheaper and fewer supporting logic chips.

8088: The Intel 8088 microprocessor was a variant of the Intel 8086 and was introduced on July 1, 1979. It had an 8-bit external data bus whereas the 8086 is 16-bit bus. The 16-bit registers and the one megabyte address range were unchanged.

8-bit bus: The type of expansion bus that can transmit 8 bits at a time.

Accelerated Graphics Port, AGP, bus: A kind of 32-bit expansion bus that runs at 66MHz. This very high-speed bus is used mainlyfor video expansion cards and can transfer data at a maximum throughput 508.6MBps.

Access time: The period of time that passes between a request for information from disk or memory and the information arriving at the requesting device. Memory access time is the time it takes to send a character from memory to or from the processor, while disk access time is the time it takes to send the read/write heads over the requested data.

Active Directory: It is a directory structure used on Microsoft Windows based computers and servers to store information and data about networks and domains.

Active hubs: It is a kind of hub using electronics to amplify and clean up the signal before it is broadcast to the other ports.

active matrix: A kind of liquid crystal display with a transistor for each pixel in the screen.

active-matrix screen: An LCD display mechanism using an individual transistor to control every pixel on the screen. Their features are high contrast, wide viewing angle, vivid colors, and fast screen refresh rates, and they do not show the streaking or shadowing that is common with cheaper LCD technology.

actuator arm: a non-volatile storage device that stores digitally encoded data on rapidly rotating rigid platters with magnetic surfaces.

address bus: The internal processor bus used for accessing memory, the width of which determines how much physical memory a processor can access.

address: The location in memory or on disk where a piece of information is stored. Every byte in memory and every sector on a disk have their own unique addresses.

Administrative Tools: It is a folder in Control Panel with tools for system administrators and advanced users.

allocation unit: a group of sectors on a magnetic disk that can be reserved for the use of a particular file.

analog: it is a device or system that represents changing values as continuously variable physical quantities. A typical analog device is a clock in which the hands move continuously around the face. Such a clock is capable of indicating every possible time of day. In contrast, a digital clock is capable of representing only a finite number of times (every tenth of a second, for example). In general, humans experience the world analogically. Vision, for example, is an analog experience because we perceive infinitely smooth gradations of shapes and colors.

anti-static bag: A bag designed to keep static charges from building up on the outside of a computer component during shipping. The bag will collect some of the charges, but does not drain them away as ESD mats do.

anti-static wrist strap or ESD strap: A specially constructed strap worn as a preventive measure to guard against the damages of ESD. One end of the strap is attached to an earth ground and the other is wrapped around the technician's wrist.

Application layer: The seventh, or highest, layer in the International Organization for Standardization's Open Systems Interconnection (ISO/OSI) model for computer-to-computer communications. This layer uses services provided by the lower layers, but is completely insulated from the details of the network hardware. It describes how application programs interact with the network operating system, including database management, e-mail, and terminal emulation programs.

ASCII: It stands for American Standard Code for Information Interchange. A standard coding scheme that assigns numeric values to letters, numbers, punctuation marks, and control characters, to achieve compatibility among different computers and peripherals.

asynchronous: The term, asynchronous, is usually used to describe communications in which data can be transmitted intermittently rather than in a steady stream. For example, a telephone conversation is asynchronous because both parties can talk whenever they like.

AT bus: Another name for the ISA bus.

ATA version 2 (ATA-2): The second version of the original IDE (ATA) specification that allowed drive sizes of several gigabtyes and overcame the limitation of 528MB. It is also sometimes generically known as Enhanced IDE (EIDE).

Attached Resource Computer Network (ARCNet): A network technology that uses a physical star, logical ring and token passing access method. It is typically wired with coaxial cable.

autoexec.bat: A contraction of AUTOmatically EXECuted BATch. It is a special DOS batch file, located in the root directory of a startup disk, and it runs automatically every time the computer is started or restarted.

auto-ranging multimeters: A multimeter that automatically sets its upper and lower ranges depending on the input signal. These multimeters are more difficult to damage by choosing the wrong range setting.

Autorun: On a CD-ROM, the Autorun option allows the CD to automatically start an installation program or a menu screen when it is inserted into the CD-ROM drive.

"baby" AT: A kind of motherboard form factor where the motherboard is smaller than the original AT form factor.

backup: Backup is the activity of copying files or databases so that they will be preserved in case of equipment failure or other catastrophe.

backup set: A related collection of backup media.

backup software: Program that is used to back up a small amount of data.

backup source: The device or data being backed up.

bandwidth: In communications, it means the difference between the highest and the lowest frequencies available for transmission in any given range, while in networking, it means the transmission capacity of a computer or a communications channel stated in megabits or megabytes per second.

batch file: File with a .bat extension that contains other DOS commands. By typing the name of the batch file and pressing Enter, DOS will process all of the batch file commands, one at a time, without need for any additional user input.

baud rate: In communications equipment, a measurement of the number of state changes (from 0 to 1 or vice versa) per second on an asynchronous communications channel.

Berg connector: A kind of connector most commonly used in PC floppy drive power cables; it has four conductors arranged in a row.

Berg connectors: A kind of power connector that is used on floppy drives.

beta: Beta code is software that has reached the stage where is usable and generally stable, but it is not completely finished. Beta code is often released to the public for testing on an "as is" basis, and user comments are then used to finish the release version of the product.

bias voltage: The high-voltage charge applied to the developing roller inside an EP cartridge.

binary: Any scheme that uses two different states, components, conditions, or conclusions. In mathematics, the binary (base-2) numbering system uses combinations of the digits 0 and 1 to represent all values.

BIOS (basic input/output system): The ROM-based software on a motherboard that acts as a kind of "interpreter" between an operating system and a computer's hardware.

BIOS CMOS setup program: Program that modifies BIOS settings in the CMOS memory. This program is available at system startup time by pressing a key combination such as Alt+F1 or Ctrl+F2.

BIOS shadow: It refers a copy of the BIOS in memory.

bit: Contraction of BInary digiT. A bit is the basic unit of information in the binary numbering system, representing either 0 (for off) or 1 (for on). Bits can be grouped together to make up larger storage units, the most common being the 8-bit byte. A byte can represent all kinds of information including the letters of the alphabet, the numbers 0 through 9, and common punctuation symbols.

bit-mapped font: A set of characters in a specific style and size, in which each character is defined by a pattern of dots. The computer must keep a complete set of bitmaps for every font you use on your system, and these bitmaps can consume large amounts of disk space.

Blue Screen of Death (BSOD): It is the error screen displayed by the Microsoft operating systems upon encountering a critical error with a non-recoverable nature, which causes the system to "crash."

boot: The loading of an operating system into memory from a hard disk, which is an automatic procedure begun when you first turn on the power of your computer. The procedure is a set of instructions contained in ROM. It first runs a series of power on self-tests (POSTs) to check if the devices are working properly and then locats and loads the operating system, and finally passes control of the computer over to that operating system.

bootable disk: Any disk capable of loading and starting the operating system.

BPS (bits per second): A measurement of how much data (how many bits) is being transmitted in one second. Typically used to describe the speed of asynchronous communications (modems).

bridge: This type of connectivity device operates in the Data Link layer of the OSI model. It is used to join similar topologies (Ethernet to Ethernet, Token Ring to Token Ring) and to divide traffic on network segments. This device will pass information destined for one particular workstation to that segment, but it will not pass broadcast traffic.

broadcasting: Sending a signal to all entities that can listen to it. In networking, it refers to sending a signal to all entities connected to that network.

brouter: It is a device combined with a network bridge and a router.

brownout: A short period of low voltage often caused by an unusually heavy demand for power.

browser: A piece of software used to access the Internet. Common browsers are Netscape's Navigator and Microsoft's Internet Explorer.

bubble-jet printer: A kind of sprayed ink printer, this type uses an electric signal that energizes a heating element, causing ink to vaporize and get pushed out of the pinhole and onto the paper.

bug: A logical or programming error in hardware or software that causes a malfunction of some sort. If the problem is in software, it can be fixed by changes to the program. If the fault is in hardware, new circuits must be designed and constructed. Some bugs are fatal and cause the program to hang or cause data loss, others are just annoying, and many are never even noticed.

bus: It is an electrical pathway through which the processor communicates with the internal and external devices attached to the computer.

bus clock: A chip on the motherboard that produces A kind of signal (called a clock signal) that indicates how fast the bus can transmit information.

bus connector slot: A slot made up of several small copper channels that grab the matching "fingers" of the expansion circuit boards. The fingers connect to copper pathways on the motherboard.

bus mastering: A technique that allows certain advanced bus architectures to delegate control of data transfers between the Central Processing Unit (CPU) and associated peripheral devices to an add-in board.

bus mouse: A mouse connected to the computer using an expansion board plugged into an expansion slot, instead of simply connected to a serial port as in the case of a serial mouse.

bus topology: Type of physical topology that consists of a single cable that runs to every workstation on the network. Each computer shares that same data and address path. As messages pass through the trunk, each workstation checks to see if the message is addressed for itself. This topology is very difficult to reconfigure, since reconfiguration requires you to disconnect and reconnect a portion of the network (thus bringing the whole network down).

byte: Contraction of BinarY digiT Eight. A group of 8 bits that, in computer storage terms, usually holds a single character, such as a number, letter, or other symbol.

cable access methods: Methods by which stations on a network get permission to transmit their data.

cache: It is a special area of memory managed by a cache controller, which is used to improve the performance by storing the contents of frequently accessed memory locations and their addresses. When the processor references a memory address, the cache checks to see if it holds that address. If it does, the information is passed directly to the processor; if not, a normal memory access takes place instead. A cache can speed up operations in a computer in which RAM access is slow compared with its processor speed, because the cache memory is always faster than normal RAM.

cache memory: Fast SRAM memory used to store, or cache, frequently used instructions and data.

capacitive keyboard: Keyboard designed with two sheets of semi-conductive material separated by a thin sheet of Mylar inside the keyboard. When a key is pressed, the plunger presses down and a paddle connected to the plunger presses the two sheets of semi-conductive material together, changing the total capacitance of the two sheets. The controller can tell by the capacitance value returned which key was pressed.

capacitive touch screen: Type of display monitor that has two clear plastic coatings over the screen, separated by air. When the user presses the screen in a particular spot, the coatings are pressed together and the controller registers a change in the total capacitance of the two layers. The controller then determines where the screen was pressed by the capacitance values and sends that information to the computer in the form of x,y coordinates.

capacitor: An electrical component used to store electrical charge.

card services: Part of the software support needed for PCMCIA (PC Card) hardware devices in a portable computer, controlling the use of system interrupts, memory, or power management. When an application wants to access a PC Card, it always goes through the card services software and never communicates directly with the underlying hardware.

carpal tunnel syndrome: A form of wrist injury caused by holding the hands in an awkward position for long periods of time.

carriage motor: Stepper motor used to move the print head back and forth on a dot-matrix printer.

cathode-ray tube: check out CRT.

CCD (charge-coupled device): A device that allows light to be converted into electrical pulses.

CCITT: It stands for Comit¨¦ Consultatif Internationale de Telephonie et de Telegraphie. An organization, based in Geneva, that develops worldwide data communications standards. CCITT is part of the ITU (International Telecommunications Union). The organization has been renamed ITU-T (ITU Telecommunications Standardization Sector).

CD-ROM: It stands for compact disc read-only memory. A high-capacity, optical storage device that uses compact disc technology to store large amounts of information, up to 650MB (the equivalent of approximately 300,000 pages of text), on a single 4.72" disk.

Central Processing Unit (CPU): The computing and control part of the computer. The CPU in a mainframe computer may be contained on many printed circuit boards, the CPU in a mini computer may be contained on several boards, and the CPU in a PC is contained in a single extremely powerful microprocessor.

centralized processing: A network processing scheme in which all "intelligence" is found in one computer and all other computers send requests to the central computer to be processed. Mainframe networks use centralized processing.

Centronics parallel interface: A standard 36-pin interface in the PC world for the exchange of information between the PC and a peripheral, such as a printer, originally developed by the printer manufacturer Centronics, Inc. The standard defines eight parallel data lines, plus additional lines for status and control information.

CGA: It stands for Color/Graphics Adapter. CGA is a video adapter that provided low-resolution text and graphics. CGA provided several different text and graphics modes, including 40- or 80-column by 25-line, 16-color text mode, and graphics modes of 640 horizontal pixels by 200 vertical pixels with 2 colors, or 320 horizontal pixels by 200 vertical pixels with 4 colors. CGA has been superseded by later video standards, including EGA, VGA, SuperVGA, and XGA.

Charge-coupled device: check out CCD (charge-coupled device).

charging corona: The wire or roller that is used to put a uniform charge on the EP drum inside a toner cartridge.

checksum: A method of providing information for error detection, usually calculated by summing a set of values.

checksumming: An error checking routine the runs a mathematical equation against a set of data and comes up with a result, called a checksum. The data is then transmitted, and the receiver then runs the same formula against the data transmitted and compares the result to the checksum. If they are the same, the transmission is considered successful.

chip creep: The slow self-loosening of chips from their sockets on the system board as a result of the frequent heating and cooling of the board (which causes parts of the board-significantly, the chip connector slots-to alternately expand and shrink).

chip puller: A tool that is used on older (pre-386) systems to remove the chips without damaging them.

cleaning step: The step in the EP print process where excess toner is scraped from the EP drum with a rubber blade.

client: A network entity that can obtain resources from the network or server.

client computers: A computer that requests resources from a network.

client software: Software that allows a device to request resources from a network.

clock doubling: Technology that allows a chip to run at the bus's rated speed externally, but still be able to run the processor's internal clock at twice the speed of the bus. This technology improves computer performance.

clock rate: check out clock speed.

clock signal: Built-in metronome-like signal that indicates how fast the components can operate.

clock speed: Also known as clock rate. The internal speed of a computer or processor, normally expressed in MHz. The faster the clock speed, the faster the computer will perform a specific operation, assuming the other components in the system, such as disk drives, can keep up with the increased speed.

clock tripling: A kind of processor design where the processor runs at one speed externally and at triple that speed internally.

cluster: The smallest unit of hard disk space that DOS can allocate to a file, consisting of one or more contiguous sectors. The number of sectors contained in a cluster depends on the hard disk type.

CMOS: It stands for Complementary Metal Oxide Semiconductor. An area of nonvolatile memory that contains settings that determine how a computer is configured.

CMOS battery: A battery used to power CMOS memory so that the computer won't lose its settings when powered down. Takes commands issued by the user through text strings or click actions and translates them back into calls that can be understood by the lower layers of DOS. It is the vital command interpreter for DOS.

Complementary Metal Oxide Semiconductor: check out CMOS.

computer name: The name by which a Microsoft computer is known on the network. This is a NetBIOS name (up to 15 characters in length) which must be unique on the network. In Windows 2000, the computer name is always the same as the machine's host name, while in Windows 9x the two can be different.

conditioning step: The step in the EP print process where a uniform charge is applied to the EP drum by the charging corona or charging roller.

conductor: Any item that permits the flow of electricity between two entities.

config.sys: In DOS and OS/2, a special text file containing settings that control the way that the operating system works. CONFIG.SYS must be located in the root directory of the default boot disk, normally drive C, and is read by the operating system only once as the system starts running. Some application programs and peripheral devices require you to include special statements in config.sys, while other commands may specify the number of disk-read buffers or open files on your system, specify how the disk cache should be configured, or load any special device drivers your system may need.

connectivity devices: Any device that facilitates connections between network devices. Some examples include hubs, routers, switches, and gateways.

Control Panel Windows panel that is used to configure the system so it is more easily usable. This control panel contains the settings for the background color and pattern as well as screen saver settings.

Control Program for Microcomputer (CP/M): A computer operating system that was an early competitor of Microsoft's DOS system. CP/M was a command-line system that was developed by Gary Kildall.

conventional memory: The first 640 KB of system memory is called conventional memory. The name refers to the fact that this is where DOS, and DOS programs, conventionally run. Originally, this was the only place that programs could run; today, despite much more memory being added to the PC, this 640 KB area remains the most important in many cases.

cooperative multitasking A form of multitasking in which all running applications must work together to share system resources. corona roller Type of transfer corona assembly that uses a charged roller to apply charge to the paper.

corona wire: Type of transfer corona assembly. Also, the wire in that assembly that is charged by the high voltage supply. It is narrow in diameter and located in a special notch under the EP print cartridge.

CPU, Central Processing Unit: check out Central Processing Unit (CPU).

CPU clock: Type of clock signal that dictates how fast the CPU can run.

crosstalk: Problem related to electromagnetic fields when two wires carrying electrical signals run parallel and one of the wires induces a signal in the second wire. If these wires are carrying data, the extra, unintended signal can cause errors in the communication. Crosstalk is especially a problem in unshielded parallel cables that are longer than 10 feet.

CRT: It stands for cathode-ray tube. A display device used in computer monitors and television sets. A CRT display consists of a glass vacuum tube that contains one electron gun for a monochrome display, or three (red, green, and blue) electron guns for a color display. Electron beams from these guns sweep rapidly across the inside of the screen from the upper-left to the lower-right of the screen. The inside of the screen is coated with thousands of phosphor dots that glow when they are struck by the electron beam. To stop the image from flickering, the beams sweep at a rate of between 43 and 87 times per second, depending on the phosphor persistence and the scanning mode used-interlaced or non-interlaced. This is known as the refresh rate and is measured in Hz. The Video Electronics Standards Association (VESA) recommends a vertical refresh rate of 72Hz, noninterlaced, at a resolution of 800 by 600 pixels.

cylinder: A hard disk consists of two or more platters, each with two sides. Each side is further divided into concentric circles known as tracks, and all the tracks at the same concentric position on a disk are known collectively as a cylinder.

daisy-chaining: Pattern of cabling where the cables run from the first device to the second, second to the third, and so on. If the devices have both an "in" and an "out," the in of the first device of each pair is connected to the out of the second device of each pair.

daisy-wheel printer: An impact printer that uses a plastic or metal print mechanism with a different character on the end of each spoke of the wheel. As the print mechanism rotates to the correct letter, a small hammer strikes the character against the ribbon, transferring the image onto the paper.

DAT: check out digital audio tape (DAT).

data bits: In asynchronous transmissions, the bits that actually comprise the data; usually 7 or 8 data bits make up the data word.

data bus: Bus used to send and receive data to the microprocessor.

data compression: Any method of encoding data so that it occupies less space than in its original form.

data encoding scheme (DES): The method used by a disk controller to store digital information onto a hard disk or floppy disk. DES has remained unbroken despite years of use; it completely randomizes the information so that it is impossible to determine the encryption key even if some of the original text is known.

Data Link layer: The second of seven layers of the International Standards Organization's Open Systems Interconnection (ISO/OSI) model for computer-to-computer communications. The Data Link layer validates the integrity of the flow of data from one node to another by synchronizing blocks of data and by controlling the flow of data.

data set ready: check out DSR.

data terminal equipment: check out DTE.

data terminal ready: check out DTR.

data transfer rate: The speed at which a disk drive can transfer information from the drive to the processor, usually measured in megabits or megabytes per second.

daughter board: A printed circuit board that attaches to another board to provide additional functions.

DB connector: Any of several types of cable connectors used for parallel or serial cables. The number following the letters DB (for data bus) indicates the number of pins that the connector usually has.

debouncing: A keyboard feature that eliminates unintended triggering of keystrokes. It works by having the keyboard controller constantly scan the keyboard for keystrokes. Only keystrokes that are pressed for more than two scans are considered keystrokes. This prevents spurious electronic signals from generating input.

dedicated server: The server that is assigned to perform a specific application or service.

default gateway: If a user needs to communicate by TCP/IP with a computer that is not on their subnet (the local network segment) the computer needs to use a gateway to access this remote network. The default gateway is simply the path that is taken by all outgoing traffic unless another path is specified.

defragmentation: The process of reorganizing and rewriting files so that they occupy one large continuous area on your hard disk rather than several smaller areas.

DES: check out data encoding scheme (DES).

Desktop: Contains the visible elements of Windows and defines the limits of the graphic environment.

developing roller: The roller inside a toner cartridge that presents a uniform line of toner to help apply the toner to the image written on the EP drum.

developing step: The step in the EP print process where the image written on the EP drum by the laser is developed, that is, it has toner stuck to it.

device driver: A small program that allows a computer to communicate with and control a device.

Device Manager: A utility in Windows 9x and Windows 2000 that allows the user to view and modify hardware settings. Device drivers can be installed or upgraded, and problems with devices can be found and dealt with here.

DEVICE=: Command found in the DOS CONFIG.SYS that tells DOS which driver to find and load into memory at boot time.

DEVICEHIGH= Command that is used to load the device drivers into upper memory blocks, thereby freeing up space in conventional memory.

diagnostic program: A program that tests computer hardware and peripherals for correct operation. In the PC, some faults are easy to find, and these are known as "hard faults"; the diagnostic program will diagnose them correctly every time. Others, such as memory faults, can be difficult to find; these are called "soft faults" because they do not occur every time the memory location is tested, but only under very specific circumstances.

differential backup: Backs up files that have changed since the last full backup. digital audio tape (DAT) A method of recording information in digital form on a small audio tape cassette. Many gigabytes of information can be recorded on a cassette, and so a DAT can be used as a backup medium. Like all tape devices, however, DATs are relatively slow.

digital signal: A signal that consists of discrete values. These values do not change over time; in effect, they change instantly from one value to another.

DIMM (Dual Inline Memory Module): Memory module that is similar to a SIMM (Single Inline Memory Module), except that a DIMM is double-sided. There are memory chips on both sides of the memory module.

DIN-n: Circular type of connector used with computers. (The n represents the number of connectors.)

DIP (Dual Inline Package): A standard housing constructed of hard plastic commonly used to hold an integrated circuit. The circuit's leads are connected to two parallel rows of pins designed to fit snugly into a socket; these pins may also be soldered directly to a printed-circuit board. If you try to install or remove dual inline packages, be careful not to bend or damage their pins.

DIP switch: A small switch used to select the operating mode of a device, mounted as a Dual Inline Package. DIP switches can be either sliding or rocker switches and are often grouped together for convenience. They are used on printed circuit boards, dot-matrix printers, modems, and other peripherals.

direct memory access: check out DMA (direct memory access).

directory: Directories are used to organize files on the hard drive. Another name for a directory is a folder. Directories created inside or below others are called "subfolders" or "subdirectories."

Direct Rambus: A memory bus that transfers data at 800MHz over a 16-bit memory bus. Direct Rambus memory models (often called RIMMs), like DDR SDRAM, can transfer data on both the rising and falling edges of a clock cycle.

direct-solder method: A method of attaching chips to the motherboard where the chip is soldered directly to the motherboard.

disk cache: An area of computer memory where data is temporarily stored on its way to or from a disk. A disk cache mediates between the application and the hard disk, and when an application asks for information from the hard disk, the cache program first checks to see if that data is already in the cache memory. If it is, the disk cache program loads the information from the cache memory rather than from the hard disk. If the information is not in memory, the cache program reads the data from the disk, copies it into the cache memory for future reference, and then passes the data to the requesting application.

disk-caching program: A program that reads the most commonly accessed data from disk and keeps it in memory for faster access.

disk controller: The electronic circuitry that controls and manages the operation of floppy or hard disks installed in the computer. A single disk controller may manage more than one hard disk; many disk controllers also manage floppy disks and compatible tape drives.

disk drive: A peripheral storage device that reads and writes to magnetic or optical disks. When more than one disk drive is installed on a computer, the operating system assigns each drive a unique name-for example A and C in DOS, Windows, and OS/2.

disk duplexing: In networking, a fault-tolerant technique that writes the same information simultaneously onto two different hard disks. Disk duplexing is offered by most of the major network operating systems and is designed to protect the system against a single disk failure; it is not designed to protect against multiple disk failures and is no substitute for a well-planned series of disk backups. diskette An easily removable and portable "floppy" disk that is 3.5" in diameter and enclosed in a durable plastic case that has a metal shutter over the media access window.

diskless workstation: A networked computer that does not have any local disk storage capability.

disk mirroring: In networking, a fault-tolerant technique that writes the same information simultaneously onto two different hard disks, using the same disk controller. In the event of one disk failing, information from the other can be used to continue operations. Disk mirroring is offered by most of the major network operating systems and is designed to protect the system against a single disk failure; it is not designed to protect against multiple disk failures and is no substitute for a well-planned series of disk backups.

Disk Operating System: check out DOS.

distributed processing: A computer system in which processing is performed by several separate computers linked by a communications network. The term often refers to any computer system supported by a network, but more properly refers to a system in which each computer is chosen to handle a specific workload and the network supports the system as a whole.

DIX Ethernet: The original name for the Ethernet network technology. Named after the original developer companies, Digital, Intel, and Xerox.

DMA, direct memory access: A method of transferring information directly from a mass-storage device such as a hard disk or from an adapter card into memory (or vice versa), without the information passing through the processor.

DMA channels: Dedicated circuit pathways on the motherboard that make DMA possible.

docking station: A hardware system into which a portable computer fits so that it can be used as a full-fledged desktop computer. Docking stations vary from simple port replicators (that allow you access to parallel and serial ports and a mouse) to complete systems (that give you access to network connections, CD-ROMs, even a tape backup system or PCMCIA ports).


1. The security structure for Windows NT Server and Windows 2000 Active Directory.
2. The namespace structure of TCP/IP's DNS structure.

Domain Name System, DNS: DNS allows TCP/IP-capable users anywhere in the world to find resources in other companies or countries by using their domain name. Each domain is an independent namespace for a particular organization, and DNS servers manage requests for information about the IP addresses of particular DNS entries. DNS is used to manage all names on the Internet.

dongle: A special cable that provides a connector to a circuit board that doesn't have one. For example, a motherboard may use a dongle to provide a serial port when there is a ribbon cable connector for the dongle on the motherboard, but there is no serial port.

dongle connection: A connector on a motherboard where a dongle will connect.

DOS: 1. It stands for Disk Operating System, an operating system originally developed by Microsoft for the IBM PC. DOS exists in two very similar versions; MS-DOS, developed and marketed by Microsoft for use with IBM-compatible computers, and PC-DOS, supported and sold by IBM for use only on computers manufactured by IBM. 2. A DOS CONFIG.SYS command that loads the operating system into conventional memory, extended memory, or into upper memory blocks on computers using the Intel 80386 or later processor. To use this command, you must have previously loaded the HIMEM.SYS device driver with the DEVICE command in config.sys.

DOS Environment Variables: Variables that specify global things like the path that DOS searches to find executables.

DOS extender: A small program that extends the range of DOS memory. For example, HIMEM.SYS allows DOS access to the memory ranges about 1024K.

DOS prompt: A visual confirmation that DOS is ready to receive input from the keyboard. The default prompt includes the current drive letter followed by a right angle bracket (for example, C>). You can create your own custom prompt with the PROMPT command.

DOS shell: An early graphic user interface for DOS that allowed users to manage files and run programs through a simple text interface and even use a mouse. It was soon replaced by Windows.

dot-matrix printer: An impact printer that uses columns of small pins and an inked ribbon to create the tiny pattern of dots that form the characters. Dotmatrix printers are available in 9-, 18-, or 24-pin configurations.

dot pitch: In a monitor, the vertical distance between the centers of like-colored phosphors on the screen of a color monitor, measured in millimeters (mm).

dots per inch (dpi): A measure of resolution expressed by the number of dots that a device can print or display in one inch.

double-density disk: A floppy disk with a storage capacity of 360KB. DRAM check out dynamic RAM (DRAM).

drawing tablet: Pointing device that includes a pencil-like device (called a stylus) for drawing on its flat rubber-coated sheet of plastic.

drive bay: An opening in the system unit into which you can install a floppy disk drive, hard disk drive, or tape drive.

drive geometry: Term used to describe the number of cylinders, read/write heads, and sectors in a hard disk.

drive hole: Hole in a floppy disk that allows the motor in the disk drive to spin the disk. Also known as the hub hole.

drive letter: In DOS, Windows, and OS/2, the drive letter is a designation used to specify a particular hard or floppy disk. For example, the first floppy disk is usually referred to as drive A, and the first hard disk as drive C.

driver: check out device driver.

driver signing: In order to prevent viruses and poorly written drivers from damaging your system, Windows 2000 uses a process called driver signing that allows companies to digitally sign their device software, and it also allows administrators to block the installation of unsigned drivers.

driver software: check out device driver.

D-Shell: check out DB connector.

DSR: It stands for data set ready. A hardware signal defined by the RS-232-C standard to indicate that the device is ready.

D-Sub: check out DB connector.

DTE: It stands for data terminal equipment. In communications, any device, such as a terminal or a computer, connected to a communications channel or public network.

DTR: It stands for data terminal ready. A hardware signal defined by the RS-232-C standard to indicate that the computer is ready to accept a transmission.

dual-booting: If a single machine must be used for many tasks, it may be necessary for it to have multiple operating systems installed simultaneously. To do this a boot manager presents the user with a choice of which operating system to use at startup. To use a different OS the user would have to shut down the system, restart it, and select the other OS.

Dual Inline Memory Module: check out DIMM (Dual Inline Memory Module).

Dual Inline Package: check out DIP (Dual Inline Package).

dumb terminal: A combination of keyboard and screen that has no local computing power, used to input information to a large, remote computer, often a minicomputer or a mainframe. This remote computer provides all the processing power for the system.

duplex: In asynchronous transmissions, the ability to transmit and receive on the same channel at the same time; also referred to as full duplex. Half-duplex channels can transmit only or receive only. Most dial-up services available to PC users take advantage of full-duplex capabilities, but if you cannot see what you are typing, switch to half duplex. If you are using half duplex and you can see two of every character you type, change to full duplex.

duplex printing: Printing a document on both sides of the page so that the appropriate pages face each other when the document is bound. dynamic electricity See electricity.

Dynamic Host Configuration Protocol (DHCP): DHCP manages the automatic assignment of TCP/IP addressing information (such as the IP address, subnet mask, default gateway and DNS server). This can save a great deal of time when configuring and maintaining a TCP/IP network.

Dynamic Link Library (DLL) files: Windows component files that contain small pieces of executable code that are shared between multiple Windows programs. They are used to eliminate redundant programming in certain Windows applications. DLLs are used extensively in Microsoft Windows, OS/2, and in Windows NT. DLLs may have filename extensions of .dll, .drv, or .fon.

dynamic RAM (DRAM): It is a type of random-access memory that stores each bit of data in a separate capacitor within an integrated circuit. The capacitor can be either charged or discharged; these two states are taken to represent the two values of a bit, conventionally called 0 and 1. Since capacitors leak charge, the information eventually fades unless the capacitor charge is refreshed periodically. Because of this refresh requirement, it is a dynamic memory as opposed to SRAM and other static memory.

edge connector: A form of connector consisting of a row of etched contacts along the edge of a printed circuit board that is inserted into an expansion slot in the computer.

EDO (Extended Data Out) RAM: A kind of DRAM that increases memory performance by eliminating wait states.

EEPROM: It stands for Electrically Erasable Programmable Read-Only Memory. A memory chip that maintains its contents without electrical power, and whose contents can be erased and reprogrammed either within the computer or from an external source. EEPROMs are used where the application requires stable storage without power but may have to be reprogrammed.

EGA: It stands for Enhanced Graphics Adapter. A video adapter standard that provides medium-resolution text and graphics. EGA can display 16 colors at the same time from a choice of 64, with a horizontal resolution of 640 pixels and a vertical resolution of 350 pixels. EGA has been superseded by VGA and SVGA.

EISA: It stands for Extended Industry Standard Architecture. A PC bus standard that extends the traditional AT-bus to 32 bits and allows more than one processor to share the bus. EISA has a 32-bit data path and, at a bus speed of 8MHz, can achieve a maximum throughput of 33 megabytes per second.

EISA Configuration Utility (EISA Config): The utility used to configure an EISA bus expansion card.

Electrically Erasable Programmable Read-Only Memory: check out EEPROM.

electromagnetic drawing tablets: Type of drawing tablet that has grids of wires underneath the rubberized surface. The stylus contains a small sensor that is sensitive to electromagnetic fields. At timed intervals, an electromagnetic pulse is sent across the grid. The sensor in the stylus picks up these pulses.

electromagnetic interference (EMI): Any electromagnetic radiation released by an electronic device that disrupts the operation or performance of any other device.

electron gun: The component of a monitor that fires electrons at the back of the phosphor-coated screen.

electrostatic discharge (ESD): When two objects of dissimilar charge come in contact with one another, they will exchange electrons in order to standardize the electrostatic charge between the two objects. This exchange, or discharge, can sometimes be seen as a spark or arc of electricity. Even when it cannot be seen it is damaging to electronic components.

email: Electronic mail is generally sent across the Internet using protocols named SMTP (for sending) and POP3 (for receiving).

EMI: check out electromagnetic interference (EMI).

emm386.exe: Reserved memory manager that emulates Expanded Memory in the Extended Memory area (XMS) and provides DOS with the ability to utilize upper memory blocks to load programs and device drivers.

encoding: Process by which binary information is changed into flux transition patterns on a disk surface.

Enhanced Graphics Adapter: check out EGA.

enhanced keyboard: A 101- or 102-key keyboard introduced by IBM that has become the accepted standard for PC keyboard layout. Unlike earlier keyboards, it has 12 function keys across the top, rather than 10 function keys in a block on the left side, has extra Ctrl and Alt keys, and has a set of cursor control keys between the main keyboard and the numeric keypad.

Enhanced Small Device Interface (ESDI): A popular hard-disk, floppy-disk, and tape-drive interface standard, capable of a data transfer rate of 10 to 20 megabits per second. ESDI is most often used with large hard disks.

environment variables: These are used to set certain system-wide parameters that can then be used by applications running on the system. For instance, a system's temporary directory can be set to a specific location using an environment variable.

EP drum: Device that is coated with a photosensitive material that can hold a static charge when not exposed to light. The drum contains a cleaning blade that continuously scrapes the used toner off the photosensitive drum to keep it clean.

EP print process: Six-step process an EP laser printer uses to form images on paper. In order, the steps are charging, exposing, developing, transferring, fusing, and cleaning.

EP printer (electrophotographic printer): Printer that uses high voltage, a laser, and a black carbon toner to form an image on a page. EPROM It stands for erasable programmable read-only memory. A memory chip that maintains its contents without electrical power, and whose contents can be erased and reprogrammed by removing a protective cover and exposing the chip to ultraviolet light.

ergonomics: Standards that define the positioning and use of the body to promote a healthy work environment.

ESD: check out electrostatic discharge (ESD).

ESD mat: Preventive measure to guard against the effects of ESD. The excess charge is drained away from any item that comes in contact with it.

Ethernet: A network technology based on the IEEE 802.3 CSMA/CD standard. The original Ethernet implementation specified 10MBps, baseband signaling, coaxial cable, and CSMA/CD media access.

even parity: A technique that counts the number of 1s in a binary number and, if the number of 1s total is not an even number, adds a digit to make it even. (check out also parity).

exit roller: Found on laser and page printers, the mechanism that guides the paper out of the printer into the paper-receiving tray. expanded memory page frame See page frame.

expanded memory specification, EMS: The original version of the Lotus-Intel-Microsoft Expanded Memory Specification (LIM EMS) that lets DOS applications use more than 640KB of memory space.

y expansion bus: An extension of the main computer bus that includes expansion slots for use by compatible adapters, such as memory boards, video adapters, hard disk controllers, and SCSI interface cards.

expansion card: A device that can be installed into a computer's expansion slot.

expansion slot: One of the connectors on the expansion bus that gives an adapter access to the system bus. You can add as many additional adapters as there are expansion slots inside your computer.

extended DOS partition: A further optional division of a hard disk, after the primary DOS partition, that functions as one or more additional logical drives. A logical drive is simply an area of a larger disk that acts as though it were a separate disk with its own drive letter.

Extended Graphics Array: check out XGA.

Extended Industry Standard Architecture: check out EISA.

extended memory manager: A device driver that supports the software portion of the extended memory specification in an IBM-compatible computer.

Extended Memory System (XMS): Memory above 1,024KB that is used by Windows and Windows-based programs. This type of memory cannot be accessed unless the HIMEM.SYS memory manager is loaded in the DOS CONFIG.SYS with a line like DEVICE=HIMEM.SYS.

extended partition: If all of the space on a drive is not used in the creation of the drive's primary partition, a second partition can be created out of the remaining space. Called the extended partition, this second partition can hold one or more logical drives.

external bus: An external component connected through expansion cards and slots allows the processor to talk to other devices. This component allows the CPU to talk to the other devices in the computer and vice versa.

external cache memory: Separate expansion board that installs in a special processor-direct bus that contains cache memory.

external commands: Commands that are not contained within COMMAND.COM. They are represented by a .COM or .EXE extension.

external hard disk: A hard disk packaged in its own case with cables and an independent power supply rather than a disk drive housed inside and integrated with the computer's system unit.

external modem: A stand-alone modem, separate from the computer and connected by a serial cable. LEDs on the front of the chassis indicate the current modem status and can be useful in troubleshooting communications problems. An external modem is a good buy if you want to use a modem with different computers at different times or with different types of computer.

FAT: check out file allocation table (FAT).

fax modem: An adapter that fits into a PC expansion slot and provides many of the capabilities of a full-sized fax machine, but at a fraction of the cost.

FDDI: check out fiber distributed data interface (FDDI).

fdisk.exe: The DOS utility that is used to partition hard disks for use with DOS.

feed roller: The rubber roller in a laser printer that feeds the paper into the printer.

fiber distributed data interface (FDDI): A specification for fiber-optic networks transmitting at a speed of up to 100 megabits per second over a dual, counter-rotating, Token Ring topology. FDDI is suited to systems that require the transfer of very large amounts of information, such as medical imaging, 3D seismic processing, oil reservoir simulation, and full-motion video.

fiber optic cable: A transmission technology that sends pulses of light along specially manufactured optical fibers. Each fiber consists of a core, thinner than a human hair, surrounded by a sheath with a much lower refractive index. Light signals introduced at one end of the cable are conducted along the cable as the signals are reflected from the sheath.

field replacement unit: check out FRU (field replacement unit).

file allocation table (FAT): A table maintained by DOS or OS/2 that lists all the clusters available on a disk. The FAT includes the location of each cluster, as well as whether it is in use, available for use, or damaged in some way and therefore unavailable. FAT also keeps track of which pieces belong to which file.

file compression program: An application program that shrinks program or data files, so that they occupy less disk space. The file must then be extracted or decompressed before you can use it. Many of the most popular file compression programs are shareware, like WinZIP, PKZIP, LHA, and StuffIt for the Macintosh, although utility packages like PC Tools from Central Point Software also contain file compression programs.

file corruption: Occasionally an improper shutdown, a virus, or a random problem will cause a file's information to become unreadable. This unreadable file is referred to as "corrupt" and it must be either repaired or replaced.

file locking: A feature of many network operating systems that prevents more than one person from updating a file at the same time by "locking" the file.

File Manager: Windows utility that allows the user to accomplish a number of important file-related tasks from a single interface. This is a Windows 3.x feature only; Window 9x uses Explorer.

file server: A networked computer used to store files for access by other client computers on the network. On larger networks, the file server may run a special network operating system; on smaller installations, the file server may run a PC operating system supplemented by peer-to-peer networking software.

file sharing: In networking, the sharing of files via the network file server. Shared files can be read, reviewed, and updated by more than one individual. Access to the file or files is often regulated by password protection, account or security clearance, or file locking, to prevent simultaneous changes from being made by more than one person at a time.

File Transfer Protocol (FTP): FTP is used to transfer large files across the Internet or any TCP/IP network. Special servers, called FTP servers, store information and then transfer it back to FTP clients as needed. FTP servers can also be secured with a username and password to prevent unauthorized downloading (retrieval of a file from the server) or uploading (placing of a file on the server).

FireWire: check out IEEE-1394.

firmware: Any software stored in a form of read-only memory-ROM, EPROM, or EEPROM-that maintains its contents when power is removed. fixed disk A disk drive that contain several disks (also known as platters) stacked together and mounted through their centers on a small rod. The disks rotate as read/write heads float above the disks that make, modify, or sense changes in the magnetic positions of the coatings on the disk.

flash memory: A special form of non-volatile EEPROM that can be erased at signal levels normally found inside the PC, so that you can reprogram the contents with whatever you like without pulling the chips out of your computer. Also, once flash memory has been programmed, you can remove the expansion board it is mounted on and plug it into another computer if you wish.

flatbed scanner: An optical device used to digitize a whole page or a large image.

flat-panel display: In laptop and notebook computers, a very narrow display that uses one of several technologies, such as electroluminescence, LCD, or thin film transistors.

floating-point calculation: A calculation of numbers whose decimal point is not fixed but moves or floats to provide the best degree of accuracy. Floatingpoint calculations can be implemented in software, or they can be performed much faster by a separate floating-point processor.

floating-point processor: A special-purpose, secondary processor designed to perform floating-point calculations much faster than the main processor.

floppy disk: A flat, round, magnetically coated plastic disk enclosed in a protective jacket. Data is written onto the floppy disk by the disk drive's read/write heads as the disk rotates inside the jacket.

floppy disk controller: The circuit board that is installed in a computer to translate signals from the CPU into signals that the floppy disk drive can understand. Often it is integrated into the same circuit board that houses the hard disk controller; it can, however, be integrated into the motherboard in the PC.

floppy disk drive: A device used to read and write data to and from a floppy disk. Floppy disk drives may be full-height drives, but more commonly these days they are half-height drives.

floppy drive cable: A cable that connects the floppy drive(s) to the floppy drive controller. The cable is a 34-wire ribbon cable that usually has three connectors. floppy drive interfaces A connector on a motherboard used to connect floppy drives to the motherboard. floptical disk A removable optical disk with a recording capacity of between 20 and 25 megabytes.

flux transition: Presence or absence of a magnetic field in a particle of the coating on the disk. As the disk passes over an area the electromagnet is energized to cause the material to be magnetized in a small area.

footprint: The amount of desktop or floor space occupied by a computer or display terminal. By extension, also refers to the size of software items such as applications or operating systems. External DOS command that prepares the partition to store information using the FAT system as required by DOS and Windows 9x. formatter board Type of circuit board that takes the information the printer receives from the computer and turns it into commands for the various components in the printer.

formatting: 1. To apply the page-layout commands and font specifications to a document and produce the final printed output. 2.The process of initializing a new, blank floppy disk or hard disk so that it can be used to store information.

form factors: Physical characteristics and dimensions of drive styles.

form feed (FF): A printer command that advances the paper in the printer to the top of the next page by pressing the FF button on the printer.

fragmentation: A disk storage problem that exists after several smaller files have been deleted from a hard disk. The deletion of files leaves the disk with areas of free disk space scattered throughout the disk. The fact that these areas of disk space are located so far apart on the disk. As a result, the storage space is used inefficiently, reducing storage capacity and in most cases reducing the performance.

free memory: An area of memory not currently used.

friction feed: A paper-feed mechanism that uses pinch rollers to move the paper through a printer, one page at a time.

FRU (field replacement unit): The individual parts or whole assemblies that can be replaced to repair a computer.

"full" AT: A kind of motherboard form factor where the motherboard is the same size as the original IBM AT computer's motherboard.

full-duplex communications: Communications where both entities can send and receive simultaneously.

function keys: The set of programmable keys on the keyboard used to perform special tasks assigned by the current application program.

fusing assembly: check out fuser.

fusing step: The step in the EP process where the toner image on the paper is fused to the paper using heat and pressure. The heat melts the toner and the pressure helps fuse the image permanently to the paper.

game port: A DB-15 connector used to connect game devices such as joysticks to a computer.

gateway: In networking, a shared connection between a local area network and a larger system, such as a mainframe computer or a large packet-switching network. Usually slower than a bridge or router, a gateway typically has its own processor and memory and can perform protocol conversions. Protocol conversion allows a gateway to connect two dissimilar networks; data is converted and reformatted before it is forwarded to the new network.

gdi.exe: Windows core component that is responsible for drawing icons and windows in Windows 3.x.

General Protection Fault (GPF): A Windows error that typically occurs when a Windows program tries to access memory currently in use by another program. gigabyte One billion bytes; however, bytes are most often counted in powers of 2, and so a gigabyte becomes 2 to the 30th power, or 1,073,741,824 bytes.

GPF: check out General Protection Fault (GPF).

graphical user interface or GUI: It allows users to select files, programs, or commands by pointing to pictorial representations on the screen rather than by typing long, complex commands from a command prompt. Application programs execute in windows, using a consistent set of pull-down menus, dialog boxes, and other graphical elements such as scroll bars and icons.

graphics accelerator board: A specialized expansion board containing a graphics coprocessor as well as all the other circuitry found on a video adapter.

graphics mode: A mode of a video card that allows the video card to display graphics.

group icons: A kind of Windows icon that groups Windows program icons together in the Program Manager.

GUI: check out graphical user interface (GUI).

half-duplex communications: Communications that occur when only one entity can transmit or receive at any one instant.

half-height drive: A space-saving drive bay that is half the height of the 3" drive bays used in the original IBM PC. Most of today's drives are half-height drives.

hand-held scanner: Type of scanner that is small enough to be held in your hand. Used to digitize a relatively small image or artwork, it consists of the controller, CCD, and light source contained in a small enclosure with wheels on it.

hard disk controller: An expansion board that contains the necessary circuitry to control and coordinate a hard disk drive. Many hard disk controllers are capable of managing more than one hard disk, as well as floppy disks and even tape drives.

hard disk drive: It is a non-volatile, random access digital data storage device. It features rotating rigid platters on a motor-driven spindle within a protective enclosure. Data is magnetically read from and written to the platter by read/write heads that float on a film of air above the platters.

hard disk interfaces: A connector on a motherboard that makes it possible to connect a hard disk to the motherboard.

hard disk system: A disk storage system containing the following components: the hard disk controller, hard disk, and host adapter.

hard memory error: A reproducible memory error that is related to hardware failure.

hard reset: A system reset made by pressing the computer's reset button or by turning the power off and then on again.

hardware: All the physical electronic components of a computer system, including peripherals, printed-circuit boards, displays, and printers.

Hardware Compatibility List (HCL): An HCL is a list (that is maintained and regularly updated by Microsoft for each of its Windows OSs) of all hardware currently known to be compatible with a particular operating system. Windows 98, NT, and 2000 all have their own HCL.

hardware interrupt: An interrupt or request for service generated by a hardware device such as a keystroke from the keyboard or a tick from the clock. Because the processor may receive several such signals simultaneously, hardware interrupts are usually assigned a priority level and processed according to that priority.

hardware ports: check out I/O address.

head: The electromagnetic device used to read from and write to magnetic media such as hard and floppy disks, tape drives, and compact discs. The head converts the information read into electrical pulses sent to the computer for processing.

header: Information that is attached to the beginning of a network data frame.

heat sink: A device that is attached to an electronic component that removes heat from the component by induction. It is often a plate of aluminum or metal with several vertical fingers.

hertz Abbreviated Hz.: A unit of frequency measurement; 1 hertz equals one cycle per second.

hexadecimal: Abbreviated hex. The base-16 numbering system that uses the digits 0 to 9, followed by the letters A to F (equivalent to the decimal numbers 10 through 15). Hex is a very convenient way to represent the binary numbers computers use internally, because it fits neatly into the 8-bit byte. All of the 16 hex digits 0 to F can be represented in 4 bits, and so two hex digits (one digit for each set of 4 bits) can be stored in a single byte. This means that 1 byte can contain any one of 256 different hex numbers, from 0 through FF. Hex numbers are often labeled with a lowercase h (for example, 1234h) to distinguish them from decimal numbers.

high-density disk: A floppy disk with more recording density and storage capacity than a double-density disk.

high-level format: The process of preparing a floppy disk or a hard disk partition for use by the operating system. In the case of DOS, a high-level format creates the boot sector, the file allocation table (FAT), and the root directory.

high memory area (HMA): In an IBM-compatible computer, the first 64K of extended memory above the 1MB limit of 8086 and 8088 addresses. Programs that conform to the extended memory specification can use this memory as an extension of conventional memory although only one program can use or control HMA at a time.

high-voltage power supply (HVPS): Provides the high voltages that are used during the EP print process. This component converts house AC currents into higher voltages that the two corona assemblies can use.

high-voltage probe: A device used to drain away voltage from a monitor before testing. It is a pencil shaped device with a metal point and a wire lead with a clip.

himem.sys: The DOS and Microsoft Windows device driver that manages the use of extended memory and the high memory area on IBM-compatible computers. HIMEM.SYS not only allows your application programs to access extended memory, it oversees that area to prevent other programs from trying to use the same space at the same time. HIMEM.SYS must be loaded by a DEVICE command in your CONFIG.SYS file; you cannot use DEVICEHIGH.

HMA: check out high memory area (HMA).

home page: On the Internet, an initial starting page. A home page may be related to a single person, a specific subject, or a corporation and is a convenient jumping-off point to other pages or resources.

host: The central or controlling computer in a networked or distributed processing environment, providing services that other computers or terminals can access via the network. Computers connected to the Internet are also described as hosts, and can be accessed using FTP, Telnet, Gopher, or a browser.

host adapter: Translates signals from the hard drive and controller to signals the computer's bus can understand.

host name: The name by which a computer is known on a TCP/IP network. This name must be unique within the domain that the machine is in. In Windows 2000 the computer name is always the same as the machine's host name, while in Windows 9x the two can be different.

hub: A connectivity device used to link several computers together into a physical star topology. They repeat any signal that comes in on one port and copies it to the other ports.

HVPS: check out high-voltage power supply (HVPS).

hybrid topology: A mix of more than one topology type used on a network.

Hypertext Transfer Protocol (HTTP): HTTP is the protocol of the World Wide Web, and is used to send and receive Web pages and other content from an HTTP server (Web server). HTTP makes use of linked pages, accessed via hyperlinks, which are words or pictures that, when clicked on, take you to another page.

I/O address: Lines on a bus used to allow the CPU to send instructions to the devices installed in the bus slots. Each device is given its own communication line to the CPU. These lines function like one-way (unidirectional) mailboxes.

I/O ports: check out I/O address.

Iaser printer: A generic name for a printer that uses the electrophotographic (EP) print process.

IBM-compatible computer: Originally, any personal computer compatible with the IBM line of personal computers. With the launch of IBM's proprietary micro channel architecture in the PS/2 line of computers, which replaced the AT bus, two incompatible standards emerged, and so the term became misleading. Now, it is becoming more common to use the term "industry-standard computer" when referring to a computer that uses the AT or ISA bus, and the term "DOS computer" to describe any PC that runs DOS and is based on one of the Intel family of chips.

IBM PC: A series of personal computers based on the Intel 8088 processor, introduced by IBM in mid-1981. The PC was released containing 16K of memory, expandable to 64K on the motherboard, and a monochrome video adapter incapable of displaying bit-mapped graphics. The floppy disk drive held 160K of data and programs. There was no hard disk on the original IBM PC; that came later with the release of the IBM PC/XT.

IBM PS/2: A series of personal computers using several different Intel processors, introduced by IBM in 1987. The main difference between the PS/2 line and earlier IBM personal computers was a major change to the internal bus. Previous computers used the AT bus, also known as industry-standard architecture, but IBM used the proprietary micro channel architecture in the PS/2 line instead. Micro channel architecture expansion boards will not work in a computer using ISA. check out IBM-compatible computer.

IC: check out integrated circuit (IC).

Icons: On-screen graphics that act as doors through which programs are started and therefore used to spawn windows. They are shortcuts that allow a user to open a program or a utility without knowing where that program is or how it needs to be configured.

IDE: It stands for integrated drive electronics. A hard disk technology that can connect multiple drives together. These drives integrate the controller and drive into one assembly. This makes them very inexpensive. Because of this, IDE drives are the most commonly used disk technology installed in computers today.

IEEE-1394: A high-speed digital interface most commonly used to transfer data between computers and digital video cameras. It has a maximum data transfer rate of over 400MBps.

illegal operation error: A Windows error that occurs when a program does something that Windows wasn't expecting or doesn't know how to do.

impact printer: Any printer that forms an image on paper by forcing a character image against an inked ribbon. Dot-matrix, daisy-wheel, and line printers are all impact printers, whereas laser printers are not. In a virtual memory system, programs and their data are divided up into smaller pieces called pages. At the point where more memory is needed, the operating system decides which pages are least likely to be needed soon (using an algorithm based on frequency of use, most recent use, and program priority), and it writes these pages out to disk. The memory space that they used is now available to the rest of the system for other application programs. When these pages are needed again, they are loaded back into real memory, displacing other pages.

incremental backup: A backup of a hard disk that consists of only those files created or modified since the last backup was performed. industry-standard architecture: check out ISA.

INI file: Text file that is created by an installation program when a new Windows application is installed. INI files contain settings for individual Windows applications as well as for Windows itself.

initialization commands: A set of commands sent to a modem to prepare it to function.

inoculating: The process of protecting a computer system against virus attacks by installing antivirus software.

input/output addresses: check out I/O address.

integrated circuit (IC): Also known as a chip. A small semiconductor circuit that contains many electronic components.

integrated drive electronics: check out IDE.

Integrated Services Digital Network: check out ISDN.

integrated system boards: A system board that has most of the computer's circuitry attached, as opposed to having been installed as expansion cards.

Intel OverDrive: OverDrive chips boost system performance by using the same clock multiplying technology found in the Intel 80486DX-2 and DX4 chips. Once installed, an OverDrive processor can increase application performance by an estimated 40 to 70 percent.

intelligent hub: A class of hub that can be remotely managed on the network.

interface: Any port or opening that is specifically designed to facilitate communication between two entities.

interface software: The software for a particular interface that translates software commands into commands that the printer can understand.

interlacing: A display technique that uses two passes over the monitor screen, painting every other line on the screen the first time and then filling in the rest of the lines on the second pass. It relies on the physiological phenomenon known as persistence of vision to produce the effect of a continuous image.

interleaving: Interleaving involves skipping sectors to write the data, instead of writing sequentially to every sector. This evens out the data flow and allows the drive to keep pace with the rest of the system. Interleaving is given in ratios. If the interleave is 2:1, the disk skips 2 minus 1, or 1 sector, between each sector it writes (it writes to one sector, skips one sector, then writes to the next sector following). Most drives today use a 1:1 interleave, because today's drives are very efficient at transferring information.

International Standards Organization (ISO): An international standard-making body, based in Geneva, that establishes global standards for communications and information exchange.

Internet: The Internet (Net) is the global TCP/IP network that now extends into nearly every office and school. The World Wide Web is the most visible part of the Internet, but e-mail, newsgroups, and FTP (to name just a few) are also important parts of the Internet.

Internet address: An IP or domain address which identifies a specific node on the Internet.

Internet Protocol: check out IP.

Internet Service Provider (ISP): An ISP is a company that provides Internet access for users. Generally ISPs are local or regional companies that provide Internet access and e-mail addresses to users.

internetwork: Any TCP/IP network that spans router interfaces is considered to be an internetwork. This means that anything from a small office with two subnets to the Internet itself can be described as an internetwork.

interrupt: It is an asynchronous signal indicating the need for attention or a synchronous event in software indicating the need for a change in execution.

interrupt request (IRQ): A hardware interrupt signals that an event has taken place to require the processor's attention, and may come from the keyboard, the input/output ports, or the system's disk drives. In the PC, the main processor does not accept interrupts from hardware devices directly; instead interrupts are routed to an Intel 8259A Programmable Interrupt Controller. This chip responds to each hardware interrupt, assigns a priority, and forwards it to the main processor.

interrupt request (IRQ) lines: Hardware lines that carry a signal from a device to the processor.

IP: It stands for Internet Protocol. The underlying communications protocol on which the Internet is based. IP allows a data packet to travel across many networks before reaching its final destination.

IP address: In order to communicate on a TCP/IP network, each machine must have a unique IP address. This address is in the form x.x.x.x where x is a number from 0 to 255.

IPCONFIG: Used on Windows 2000 to view current IP configuration information and to manually request updated information from a DHCP server.

IRQ: check out interrupt request (IRQ).

ISA: It stands for industry-standard architecture. The 16-bit bus design was first used in IBM's PC/AT computer in 1984. ISA has a bus speed of 8MHz and a maximum throughput of 8 megabytes per second. EISA is a 32-bit extension to this standard bus.

ISDN: It stands for Integrated Services Digital Network. A worldwide digital communications network emerging from existing telephone services, intended to replace all current systems with a completely digital transmission system. Computers and other devices connect to ISDN via simple, standardized interfaces, and when complete, ISDN systems will be capable of transmitting voice, video, music, and data. joystick port check out game port.

jumper: A small plastic and metal connector that completes a circuit, usually to select one option from a set of several user-definable options. Jumpers are often used to select one particular hardware configuration rather than another.

kernel file: Windows core component that is responsible for managing Windows resources and running applications.

kilobit: Abbreviated Kb or Kbit. 1024 bits (binary digits).

kilobits per second: Abbreviated Kbps. The number of bits, or binary digits, transmitted every second, measured in multiples of 1024 bits per second. Used as an indicator of communications transmission rate.

kilobyte: Abbreviated K, KB, or Kbyte. 1024 bytes.

L1 Cache: Any cache memory that is integrated into the CPU.

L2 Cache: Any cache memory that is external to the CPU.

L3 Cache: It is specialized memory that works hand-in-hand with L1 and L2 cache to improve computer performance.

LAN: check out local area network, LAN.

laser scanner: The assembly in an EP process printer that contains the laser. This component is responsible for writing the image to the EP drum. latency The time that elapses between issuing a request for data and actually starting the data transfer. In a hard disk, this translates into the time it takes to position the disk's read/write head and rotate the disk so that the required sector or cluster is under the head. Latency is just one of many factors that influence disk access speeds.

LCD: check out liquid crystal display (LCD).

LCD monitor: A monitor that uses liquid crystal display technology. Many laptop and notebook computers use LCD displays because of their low power requirements. least significant bit (LSB) In a binary number, the lowest-order bit. That is, the rightmost bit. So, in the binary number 0001, the 1 is the least significant bit.

LED page printer: A kind of EP process printer that uses a row of LEDs instead of a laser to expose the EP drum.

legacy: A component that is still functional but is out of date.

letter quality, LQ: A category of dot-matrix printer that can print characters that look very close to the quality a laser printer might produce.

liquid crystal display, LCD: A display technology common in portable computers that uses electric current to align crystals in a special liquid. The rodshaped crystals are contained between two parallel transparent electrodes, and when current is applied, they change their orientation, creating a darker area. Many LCD screens are also backlit or side-lit to increase visibility and reduce the possibility of eyestrain.

local area network, LAN: A group of computers and associated peripherals connected by a communications channel capable of sharing files and other resources between several users.

local bus: A PC bus specification that allows peripherals to exchange data at a rate faster than the 8 megabytes per second allowed by the ISA (Industry Standard Architecture) and the 32 megabytes per second allowed by the EISA (Extended Industry Standard Architecture) definitions. Local bus can achieve a maximum data rate of 133 megabytes per second with a 33MHz bus speed, 148 megabytes per second with a 40MHz bus, or 267 megabytes per second with a 50MHz bus.

logic board: The sturdy sheet or board to which all other components on the computer are attached. These components consist of the CPU, underlying circuitry, expansion slots, video components, and RAM slots, just to name a few. Also known as a motherboard or planar board.

logical drive: Created within an extended partition, a logical drive is used to organize space within the partition, which can be accessed through the use of a drive letter.

logical memory: The way memory is organized so it can be accessed by an operating system.

logical topology: Topology that defines how the data flows in a network.

login: The process of logging on submits your username and password to the network and gives you the network credentials you will use for the rest of that session. Users can either log on to a workgroup or to a network security entity (such as the Active Directory).

low-level format: The process that creates the tracks and sectors on a blank hard disk or floppy disk; sometimes called the physical format. Most hard disks are already low-level formatted; however, floppy disks receive both a low- and a high-level format (or logical format) when you use the DOS or OS/2 command FORMAT.

LPTx ports: In DOS, the device name used to denote a parallel communications port, often used with a printer. DOS supports three parallel ports: LPT1, LPT2, and LPT3, and OS/2 adds support for network ports LPT4 through LPT9. magneto-optical (MO) drives An erasable, high-capacity, removable storage device similar to a CD-ROM drive. Magneto-optical drives use both magnetic and laser technology to write data to the disk and use the laser to read that data back again. Writing data takes two passes over the disk, an erase pass followed by the write pass, but reading can be done in just one pass and, as a result, is much faster.

main motor: A printer stepper motor that is used to advance the paper. master drive The primary drive in an IDE master/slave configuration. math coprocessor A processor that speeds up the floating decimal point calculations that are needed in algebra and statistical calculations.

MCA: MCA is incompatible with expansion boards that follow the earlier 16-bit AT bus standard, physically because the boards are about 50 percent smaller and electronically as the bus depends on more proprietary integrated circuits. MCA was designed for multiprocessing, and it also allows expansion boards to identify themselves, thus eliminating many of the conflicts that arose through the use of manual settings in the original bus.

Megabit (Mbit): Usually 1,048,576 binary digits or bits of data. Often used as equivalent to 1 million bits.

megabits per second (Mbps): A measurement of the amount of information moving across a network or communications link in 1 second, measured in multiples of 1,048,576 bits.

Megabyte (MB): Usually 1,048,576 bytes. Megabytes are a common way of representing computer memory or hard-disk capacity.

Megahertz (MHz): One million cycles per second. A processor's clock speed is often expressed in MHz. The original IBM PC operated an 8088 running at 4.77MHz, while the more modern Pentium processor runs at speeds of up to 1000MHz and higher.

memory: The primary random access memory (RAM) installed in the computer. The operating system copies application programs from disk into memory, where all program execution and data processing takes place; results are written back out to disk again. The amount of memory installed in the computer can determine the size and number of programs that it can run, as well as the size of the largest data file.

memory address: The exact location in memory that stores a particular data item or program instruction.

memory map: The organization and allocation of memory in a computer. A memory map will give an indication of the amount of memory used by the operating system and the amount remaining for use by applications.

memory optimization: The process of making the most possible conventional memory available to run DOS programs.

memory refresh: An electrical signal that keeps the data stored in memory from degrading.

mesh topology: Type of logical topology where each device on a network is connected to every other device on the network. This topology uses routers to search multiple paths and determine the best path.

Messaging Application Programming Interface (MAPI): The MAPI interface is used to control how Windows interacts with messaging applications such as e-mail programs. MAPI makes most of the functions of e-mail transparent and allows programmers to just write the application, not the whole messaging system.

MFM encoding: check out modified frequency modulation (MFM) encoding.

Microsoft Diagnostics: check out MSD (Microsoft Diagnostics).

Microsoft Disk Operating System: check out MS-DOS.

modem: It stands for modulator/demodulator. It is a device that allows a computer to transmit information over a telephone line. The modem translates between the digital signals that the computer uses and analog signals suitable for transmission over telephone lines. When transmitting, the modem modulates the digital data onto a carrier signal on the telephone line. When receiving, the modem performs the reverse process and demodulates the data from the carrier signal.

modified frequency modulation (MFM) encoding: The most widely used method of storing data on a hard disk. Based on an earlier technique known as frequency modulation (FM) encoding, MFM achieves a two-fold increase in data storage density over standard FM recording, but it is not as efficient a space saver as run-length limited encoding.

Molex connector: check out standard peripheral power connector.

monitor: A video output device capable of displaying text and graphics, often in color.

monochrome monitor: A monitor that can display text and graphics in one color only. For example, white text on a green background or black text on a white background.

most significant bit (MSB): In a binary number, the highest-order bit. That is, the leftmost bit. In the binary number 10000000, the 1 is the most significant bit.

motherboard: The main printed circuit board in a computer that contains the central processing unit, appropriate coprocessor and support chips, device controllers, memory, and also expansion slots to give access to the computer's internal bus. Also known as a logic board or system board.

mouse: A small input device with one or more buttons used as for pointing or drawing. As you move the mouse in any direction, an on-screen mouse cursor follows the mouse movements; all movements are relative. Once the mouse pointer is in the correct position on the screen, you can press one of the mouse buttons to initiate an action or operation; different user interfaces and file programs interpret mouse clicks in different ways.

msbackup: A DOS program that allows the user to make backup copies of all the programs and data stored on the hard disk. This program is menu-driven and allows the user to set up options that can be used each time you back up the hard drive.

MSD (Microsoft Diagnostics): Program that allows the user to examine many different aspects of a system's hardware and software setup.

MS-DOS: It stands for Microsoft Disk Operating System. MS-DOS, like other operating systems, allocates system resources (such as hard and floppy disks, the monitor, and the printer) to the applications programs that need them. MS-DOS is a single-user, single-tasking operating system, with either a command-line interface or a shell interface.

multimedia: A computer technology that displays information by using a combination of full-motion video, animation, sound, graphics, and text with a high degree of user interaction.

multiplexer: A network device that combines multiple data streams into a single stream for transmission. Multiplexers can also break out the original data streams from a single, multiplexed stream.

multipurpose server: A server that has more than one use. For example, a multi-purpose server can be both a file server and a print server. multistation access unit (MAU) The central device in a Token Ring network that provides both the physical and logical connections to the stations.

multisync monitor: A monitor designed to detect and adjust to a variety of different input signals. By contrast, a fixed-frequency monitor must receive a signal at one specific frequency.

multitasking: A feature of an operating system that allows more than one program to run at the same time.

multithreading: The ability of a program to send multiple tasks to the processor at the same time. This allows an application to execute more quickly, but it requires the support of a multithreaded operating system.

near letter quality (NLQ): A category of dot-matrix printer that can come close to the quality of a laser printer, but still is lacking somewhat in print quality.

NetBEUI: It stands for NetBIOS Extended User Interface. A network device driver for the transport layer supplied with Microsoft's LAN Manager.

NetBIOS: It stands for Network Basic Input/Output System. In networking, a layer of software, originally developed in 1984 by IBM and Sytek, that links a network operating system with specific network hardware. NetBIOS provides an application program interface (API) with a consistent set of commands for requesting lower-level network services to transmit information from node to node.

NetBIOS Extended User Interface: check out NetBEUI.

network: A group of computers and associated peripherals connected by a communications channel capable of sharing files and other resources between several users. A network can range from a peer-to-peer network (that connects a small number of users in an office or department) to a local area network (that connects many users over permanently installed cables and dial-up lines) or to a wide area network (that connects users on several different networks spread over a wide geographic area).

network adapter: In order to access network resources, a physical connection to the network must be made. This is generally done through the network adapter, which is expansion hardware designed to interface with the network.

Network Basic Input/Output System: check out NetBIOS.

network client software: The software that enables a computer to communicate on the network.

network interface card (NIC): In networking, the PC expansion board that plugs into a personal computer or server and works with the network operating system to control the flow of information over the network. The network interface card is connected to the network cabling (twisted-pair, coaxial or fiber-optic cable), which in turn connects all the network interface cards in the network.

Network layer: The third of seven layers of the International Standards Organization's Open Systems Interconnection (ISO/OSI) model for computer-tocomputer communications. The Network layer defines protocols for data routing to ensure that the information arrives at the correct destination node. network security provider In a network environment, it is often easier to manage the network by having centralized user ID and password storage. Examples of this type of centralized system are Windows 2000's Active Directory or NetWare's NDS.

NIC: check out network interface card (NIC).

node: In communications, any device attached to the network.

non-dedicated server: A computer that can be both a server and a workstation. In practice, by performing the functions of both server and workstation, this type of server does neither function very well. Nondedicated servers are typically used in peer-to-peer networks. nonintegrated system boards A kind of motherboard where the various subsystems (video, disk access, etc.) are not integrated into the motherboard, but rather placed on expansion cards that can be removed and upgraded.

non-interlaced: Describes a monitor in which the display is updated (refreshed) in a single pass, painting every line on the screen. Interlacing takes two passes to paint the screen, painting every other line on the first pass, and then sequentially filling in the other lines on the second pass. Non-interlaced scanning, while more expensive to implement, reduces unwanted flicker and eyestrain.

NOS (Network Operating System): Software that runs on the server and controls and manages the network. The NOS controls the communication with resources and the flow of data across the network.

notebook computer: A small portable computer, about the size of a computer book, with a flat screen and a keyboard that fold together. A notebook computer is lighter and smaller than a laptop computer. Some models use flash memory rather than conventional hard disks for program and data storage, while other models offer a range of business applications in ROM. Many offer PCMCIA expansion slots for additional peripherals such as modems, fax modems, or network connections.

NTFS: The NT File System was created to provide enhanced security and performance for the Windows NT operating system, and it has been adopted and improved upon by Windows 2000. NTFS provides Windows 2000 with local file security, file auditing, compression, and encryption options. It is not compatible with Windows 9x or DOS.

null modem: A short RS-232-C cable that connects two personal computers so that they can communicate without the use of modems. The cable connects the two computers' serial ports, and certain lines in the cable are crossed over so that the wires used for sending data by one computer are used for receiving data by the other computer and vice versa.

numeric keypad: A set of keys to the right of the main part of the keyboard, used for numeric data entry.

odd parity: A technique that counts the number of 1s in a binary number and, if the number of 1s total is not an odd number, adds a digit to make it odd. check out also parity.

Open Systems Interconnection, OSI, model: check out OSI, Open Systems Interconnection, model.

operating system (OS): The software responsible for allocating system resources, including memory, processor time, disk space, and peripheral devices such as printers, modems, and the monitor. All application programs use the operating system to gain access to these system resources as they are needed. The operating system is the first program loaded into the computer as it boots, and it remains in memory at all times thereafter.

optical disk: A disk that can be read from and written to, like a fixed disk but, like a CD, is read with a laser.

optical drive: A kind of storage drive that uses a laser to read from and write to the storage medium.

optical mouse: A mouse that uses a special mouse pad and a beam of laser light. The beam of light shines onto the mouse pad and reflects back to a sensor in the mouse. Special small lines crossing the mouse pad reflect the light into the sensor in different ways to signal the position of the mouse.

optical scanner: check out scanner.

optical touch screen: A kind of touch screen that uses light beams on the top and left side and optical sensors on the bottom and right side to detect the position of your finger when you touch the screen.

option diskette: A diskette that contains the device-specific configuration files for the device being installed into a MCA bus computer.

OSI, Open Systems Interconnection, model: A protocol model, developed by the International Standards Organization (ISO), that was intended to provide a common way of describing network protocols. This model describes a seven-layered relationship between the stages of communication. Not every protocol maps perfectly to the OSI model, as there is some overlap within some the layers of some protocols. page description language Describes the whole page being printed. The controller in the printer interprets these commands and turns them into laser pulses or firing print wires.

page frame: The special area reserved in upper memory that is used to swap pages of memory into and out of expanded memory.

page printers: Type of printer that handles print jobs one page at a time instead of one line at a time. pages 16K chunks of memory used in expanded memory.

paging: The process of swapping memory to an alternate location, such as to and from a page frame in expanded memory or to and from a swap file.

paper pickup roller: A D-shaped roller that rotates against the paper and pushes one sheet into the printer.

paper registration roller: A roller in an EP process printer that keeps paper movement in sync with the EP image formation process.

paper transport assembly: The set of devices that moves the paper through the printer. It consists of a motor and several rubberized rollers that each perform a different function.

parallel port: An input/output port that manages information 8 bits at a time, often used to connect a parallel printer.

parallel processing: A processor architecture where a processor essentially contains two processors in one. The processor can then execute more than one instruction per clock cycle.

parity: Parity is a simple form of error checking used in computers and telecommunications. Parity works by adding an additional bit to a binary number and using it to indicate any changes in that number during transmission.

partition: A portion of a hard disk that the operating system treats as if it were a separate drive.

partition table: In DOS, an area of the hard disk containing information on how the disk is organized. The partition table also contains information that tells the computer which operating system to load; most disks will contain DOS, but some users may divide their hard disk into different partitions, or areas, each containing a different operating system. The partition table indicates which of these partitions is the active partition, the partition that should be used to start the computer.

passive hub: Type of hub that electrically connects all network ports together. This type of hub is not powered.

passive-matrix screen: An LCD display mechanism that uses a transistor to control every row of pixels on the screen. This is in sharp contrast to activematrix screens, where each individual pixel is controlled by its own transistor.

path: When referring to a file on a computer's hard drive, the path is used to describe where it exists within the directory structure. If a file is on the C drive in a folder named my_doc, its path is c:\my_doc\.

PC Card: A PC Card, also known as a PCMCIA card or a "credit card adapter" is a peripheral device that uses the PCMCIA specification. These have the advantage of being small, easy to use and fully plug-and-play compliant.

PC Card slot: An opening in the case of a portable computer intended to receive a PC Card; also known as a PCMCIA slot.

PC Card Socket: Services check out socket services.

PCB: check out printed-circuit board, PCB.

PCI: It stands for Peripheral Component Interconnect. A specification introduced by Intel that defines a local bus that allows up to 10 PCI-compliant expansion cards to be plugged into the computer. One of these 10 cards must be the PCI controller card, but the others can include a video card, network interface card, SCSI interface, or any other basic input/output function. The PCI controller exchanges information with the computer's processor as 32- or 64-bits and allows intelligent PCI adapters to perform certain tasks concurrently with the main processor by using bus mastering techniques.

PCMCIA: It stands for PC Memory Card International Association. Expansion cards developed for this standard are now called PC Cards.

peer-to-peer network: Network where the computers act as both workstations and servers and where there is no centralized administration or control.

Pentium: The Pentium represents the evolution of the 80486 family of microprocessors and adds several notable features, including 8K instruction code and data caches, built-in floating-point processor and memory management unit, as well as a superscalar design and dual pipelining that allow the Pentium to execute more than one instruction per clock cycle.

Pentium Pro: The 32-bit Pentium Pro (also known as the P6) has a 64-bit data path between the processor and cache and is capable of running at clock speeds up to 200MHz. Unlike the Pentium, the Pentium Pro has its secondary cache built into the CPU itself, rather than on the motherboard, meaning that it accesses cache at internal speed, not bus speed.

peripheral: Any hardware device attached to and controlled by a computer, such as a monitor, keyboard, hard disk, floppy disk, CD-ROM drives, printer, mouse, tape drive, and joystick.

Peripheral Component Interconnect: check out PCI.

permanent swap file: A permanent swap file allows Microsoft Windows to write information to a known place on the hard disk, which enhances performance over using conventional methods with a temporary swap file. The Windows permanent swap file consists of a large number of consecutive contiguous clusters; it is often the largest single file on the hard disk, and of course this disk space cannot be used by any other application.

PGA (Pin Grid Array): A kind of IC package that consists of a grid of pins connected to a square, flat package.

photosensitive drum: check out EP drum.

Physical layer: The first and lowest of the seven layers in the International Standards Organization's Open Systems Interconnection (ISO/OSI) model for computer-to-computer communications. The Physical layer defines the physical, electrical, mechanical, and functional procedures used to connect the equipment.

physical topology: A description that identifies how the cables on a network are physically arranged.

pickup roller: check out paper pickup roller.

Pin Grid Array: check out PGA (Pin Grid Array).

ping: It is a utility used to send a short message to another computer on a TCP/IP network. PING can be useful troubleshooting tool to test connectivity between networks or to check out if a particular machine is communicating with the network.

pixel: It is the smallest addressable screen element in a display device or it is the smallest unit of picture that can be represented or controlled. Each pixel has its own address. The address of a pixel corresponds to its coordinates. Pixels are normally arranged in a two-dimensional grid, and are often represented using dots or squares.

planar board: check out motherboard.

platform: An operating system (OS) is the basic software that runs on a computer, and it is the base on which all other software sits. As such the OS is the "platform" that applications and utilities run on.

Plug and Play (PnP): A standard that defines automatic techniques designed to make PC configuration simple and straightforward.

POST: check out power on self-test (POST).

Post Office Protocol v 3 (POP3): POP3 is used to accept and store e-mail and to allow users to connect to their mailbox and access their mail. SMTP is used to send mail to the POP3 server.

PostScript: A page-description language used when printing high-quality text and graphics. Desktop publishing or illustration programs that create PostScript output can print on any PostScript printer or imagesetter, because PostScript is hardware-independent. An interpreter in the printer translates the PostScript commands into commands that the printer can understand.

potentiometer: check out variable resistor.

power on self-test (POST): A set of diagnostic programs, loaded automatically from ROM BIOS during startup, designed to ensure that the major system components are present and operating. If a problem is found, the POST software writes an error message in the screen, sometimes with a diagnostic code number indicating the type of fault located. These POST tests execute before any attempt is made to load the operating system.

power supply: A part of the computer that converts the power from a wall outlet into the lower voltages, typically 5 to 12 volts DC, required internally in the computer.

power surge: A brief but sudden increase in line voltage, often destructive, usually caused by a nearby electrical appliance (such as a photocopier or elevator) or when power is reapplied after an outage.

power users: A power user is someone who either does administrative-level tasks on their machine or needs to have additional access to the system to do their work. The Power Users group on a Windows 2000 Professional station has abilities somewhere between normal users and administrators.

preemptive multitasking: A form of multitasking where the operating system executes an application for a specific period of time, according to its assigned priority and need. At that time, it is preempted and another task is given access to the CPU for its allocated time. Although an application can give up control before its time is up, such as during input/output waits, no task is ever allowed to execute for longer than its allotted time period.

Presentation layer: The sixth of seven layers of the International Standards Organization's Open Systems Interconnection (ISO/OSI) model for computerto-computer communications. The Presentation layer defines the way that data is formatted, presented, converted, and encoded. preventative maintenance The process of performing various procedures on a computer to prevent future data loss or system downtime.

primary DOS partition: In DOS, a division of the hard disk that contains important operating system files. A DOS hard disk can be divided into two partitions, or areas: the primary DOS partition and the extended DOS partition. If you want to start your computer from the hard disk, the disk must contain an active primary DOS partition that includes the three DOS system files: MSDOS.SYS, IO.SYS, and COMMAND.COM. The primary DOS partition on the first hard disk in the system is referred to as drive C. Disk partitions are displayed, created, and changed using the FDISK command.

print consumables: Products that a printer uses in the print process that must be replaced occasionally. Examples include toner, ink, ribbons, and paper.

printed-circuit board (PCB): Any flat board made of plastic or fiberglass that contains chips and other electronic components. Many PCBs are multilayer boards with several different sets of copper traces connecting components together.

printer control assembly: Large circuit board in the printer that converts signals from the computer into signals for the various parts in the laser printer.

printer ribbon: A fabric strip that is impregnated with ink and wrapped around two spools encased in a cartridge. This cartridge is used in dot-matrix printers to provide the ink for the print process.

printhead: That part of a printer that creates the printed image. In a dot-matrix printer, the printhead contains the small pins that strike the ribbon to create the image, and in an ink-jet printer, the printhead contains the jets used to create the ink droplets as well as the ink reservoirs. A laser printer creates images using an electrophotographic method similar to that found in photocopiers and does not have a printhead.

print media: Another name for the mediums being printed on. Examples include paper, transparencies, and labels.

product key: Software piracy is a serious problem in the industry, so many programs include a product key that must be typed in for the software to install properly. This key is then submitted if the user registers for technical support.

productivity tools: Any of a number of applications users depend on to do jobrelated tasks. Word processors and spreadsheets are common examples, but most companies have additional productivity tools as well.

Program Groups: check out group icons.

Program Manager Group (GRP): Files in the Windows 3.x directories that store information about which application icons are contained in which group icons.

Program Manager: The primary interface to Windows that allows you to organize and execute numerous programs by double-clicking an icon in a single graphical window. proprietary design: A motherboard design that is unique to a particular manufacturer and is not licensed to other manufacturers.

protected mode: A processor operating mode where every program's memory is protected from every other program so that if one program crashes, it doesn't bring down the other programs.

protocol: In networking and communications, the specification that defines the procedures to follow when transmitting and receiving data. Protocols define the format, timing, sequence, and error-checking systems used.

protocol stack: In networking and communications, the several layers of software that define the computer-to-computer or computer-to-network protocol. The protocol stack on a Novell NetWare system will be different from that used on a Banyan VINES network or on a Microsoft LAN Manager system.

PS/2 mouse interface: A kind of mouse interface that uses a round, DIN-6 connector that gets its name from the first computer it was introduced on, the IBM PS/2.

puck: The proper name for the mouse-like device used with drawing tablets.

QSOP (Quad Small Outline Package): A kind of IC package that has all leads soldered directly to the circuit board. Also called a "surface mount" chip.

Quick-and-Dirty Disk Operating System (QDOS): Created by Tim Patterson of Seattle Computer Products, QDOS was the basis of MS-DOS. QDOS was purchased by Microsoft and renamed MS-DOS.

radio frequency interference (RFI): Many electronic devices, including computers and peripherals, can interfere with other signals in the radio-frequency range by producing electromagnetic radiation; this is normally regulated by government agencies in each country.

RAM: It stands for random access memory. The main system memory in a computer, used for the operating system, application programs, and data.

RAM disk: An area of memory managed by a special device driver and used as a simulated disk. Anything stored on a RAM disk will be erased when the computer is turned off; therefore, the contents must be saved onto a real disk.

Rambus Inline Memory Modules (RIMMs): A kind of memory module that uses Rambus memory. check out Direct Rambus.

random access memory: check out RAM.

rasterizing: The process of converting signals from the computer into signals for the various assemblies in the laser printer.

read-only memory: check out ROM (read-only memory).

read/write head: That part of a floppy- or hard-disk system that reads and writes data to and from a magnetic disk.

real mode: A processor operating mode whereby a processor emulates an 8086 processor.

reference disk: A special disk that is bootable and contains a program that is able to send special commands to MCA bus devices to configure their parameters.

refresh rate: In a monitor, the rate at which the phosphors that create the image on the screen are recharged.

registration roller: check out paper registration roller.

Registry: The Registry is used in Windows 9x, NT, and 2000 to store configuration information about the machine. This includes information about both individual user settings and global system settings.

REM statement: A command placed in the beginning of a line in a DOS batch file to prevent that line from executing.

removable mass storage: Any high-capacity storage device inserted into a drive for reading and writing, then removed for storage and safekeeping.

removable media: Any storage media that can be removed from the system.

repeater: In networking, a simple hardware device that moves all packets from one local area network segment to another.

reserved memory: In DOS, a term used to describe that area of memory between 640K and 1MB, also known as upper memory. Reserved memory is used by DOS to store system and video information.

resource: Anything on a network that clients might want to access or use. restore The process of getting data from a backup restored to the computer it originally came from.

RFI: check out radio frequency interference (RFI).

ribbon cartridge: The container that holds the printer ribbon.

ring topology: Type of physical topology in which each computer connects to two other computers, joining them in a circle and creating a unidirectional path where messages move from workstation to workstation. Each entity participating in the ring reads a message, regenerates it, and then hands it to its neighbor.

RJ-11/RJ-45: A commonly used modular telephone connector. RJ-11 is a four- or six-pin connector used in most connections destined for voice use; it is the connector used on phone cords. RJ-45 is the eight-pin connector used for data transmission over twisted-pair wiring and can be used for networking; RJ-45 is the connector used on 10Base-T Ethernet cables.

RLL encoding: check out run-length limited (RLL) encoding.

ROM (read-only memory): A kind of computer memory that retains its data permanently, even when power is removed. Once the data is written to this type of memory, it cannot be changed.

root directory: In a hierarchical directory structure, the directory from which all other directories must branch. The root directory is created by the FORMAT command and can contain files as well as other directories. This directory cannot be deleted.

router: In networking, an intelligent connecting device that can send packets to the correct local area network segment to take them to their destination. Routers link local area network segments at the network layer of the International Standards Organization's Open Systems Interconnect (ISO/OSI) model for computerto-computer communications.

RS-232-C: In asynchronous transmissions, a recommended standard interface established by the Electrical Industries Association. The standard defines the specific lines, timing, and signal characteristics used between the computer and the peripheral device and uses a 25-pin or 9-pin DB connector. RS-232-C is used for serial communications between a computer and a peripheral such as a printer, modem, digitizing tablet, or mouse.

RS-232 cables: check out serial cables.

RS-422/423/449: In asynchronous transmissions, a recommended standard interface established by the Electrical Industries Association for distances greater than 50 feet but less than 1000 feet. The standard defines the specific lines, timing, and signal characteristics used between the computer and the peripheral device.

RTS: It stands for request to send. A hardware signal defined by the RS-232-C standard to request permission to transmit.

run-length limited (RLL) encoding: An efficient method of storing information on a hard disk that effectively doubles the storage capacity of a disk when compared to older, less efficient methods such as modified frequency modulation encoding (MFM).

Safe Mode: A Windows 9x operating mode that only loads a basic set of drivers and a basic screen resolution. It can be activated using the F8 key at boot time. scanner An optical device used to digitize images such as line art or photographs, so that they can be merged with text by a page-layout or desktop publishing program or incorporated into a CAD drawing.

screen saver: Program originally designed to prevent damage to a computer monitor from being left on too long. These programs usually include moving graphics so that no one pixel is left on all the time. Screen savers detect computer inactivity and activate after a certain period.

SCSI: It stands for small computer system interface. A high-speed, system-level parallel interface defined by the ANSI X3T9.2 committee. SCSI is used to connect a personal computer to several peripheral devices using just one port. Devices connected in this way are said to be "daisy-chained" together, and each device must have a unique identifier or priority number.

SCSI adapter: Device that is used to manage all the devices on the SCSI bus as well as to send and retrieve data from the devices.

SCSI address: A unique address given to each SCSI device.

SCSI bus: Another name for the SCSI interface and communications protocol.

SCSI chain: All the devices connected to a single SCSI adapter.

SCSI terminator: The SCSI interface must be correctly terminated to prevent signals echoing on the bus. Many SCSI devices have built-in terminators that engage when they are needed. With some older SCSI devices, you have to add an external SCSI terminator that plugs into the device's SCSI connector.

sector: The smallest unit of storage on a disk, usually 512 bytes. Sectors are grouped together into clusters.

seek time: Time it takes the actuator arm to move from rest position to active position for the read/write head to access the information. Often used as a performance gauge of an individual drive. The major part of a hard disk's access time is actually seek time.

semiconductors: Any material that, depending on some condition, is either a conductor or non-conductor.

serial cables: Cables used for serial communications. check out serial communications.

serial communications: The transmission of information from computer to computer or from computer to a peripheral, one bit at a time. Serial communications can be synchronous and controlled by a clock or asynchronous and coordinated by start and stop bits embedded in the data stream.

serial mouse: A mouse that attaches directly to one of the computer's serial ports.

serial port: A computer input/output port that supports serial communications in which information is processed one bit at a time. RS-232-C is a common serial protocol used by computers when communicating with modems, printers, mice, and other peripherals.

serial printer: A printer that attaches to one of the computer's serial ports.

server: In networking, any computer that makes access to files, printing, communications, or other services available to users of the network. In large networks, a server may run a special network operating system; in smaller installations, a server may run a personal computer operating system.

service: A service is any program that runs in the background on a computer and performs some sort of task for that computer or other machines on the network.

Session layer: The fifth of seven layers of the International Standards Organization's Open Systems Interconnection (ISO/OSI) model for computer-tocomputer communications. The Session layer coordinates communications and maintains the session for as long as it is needed, performing security, logging, and administrative functions.

share name: The share name is used to identify a network access point. Share names can be the same as the directory they are sharing or they can be different. shell Every operating system needs to have some sort of interface that allows users to navigate the system. The shell is the program that controls how this interface works. For MS-DOS, the Windows Program Manager was its most popular shell. For Windows 9x and 2000, Explorer (explorer.exe) is the standard shell program.

shielded twisted-pair: check out STP (shield twisted-pair).

Simple Mail Transport Protocol (SMTP): SMTP is used to send mail from a client to an e-mail server. SMTP servers do not store mail for users to pick up; they simply send the mail out, and another server (such as a POP3 server) is used to store incoming mail.

Single Inline Memory Module (SIMM): Individual RAM chips are soldered or surface mounted onto small narrow circuit boards called carrier modules, which can be plugged into sockets on the motherboard. These carrier modules are simple to install and occupy less space than conventional memory modules.

Single Inline Package (SIP): A kind of semiconductor package where the package has a single row of connector pins on one side only. single-purpose server A server that is dedicated to one purpose (e.g., a file server or a printer server).

site license: A software license that is valid for all installations at a single site. slave drive The secondary drive in a IDE master/slave disk configuration.

small computer system interface: check out SCSI.

socket services: Part of the software support needed for PCMCIA hardware devices in a portable computer, controlling the interface to the hardware. Socket services is the lowest layer in the software that manages PCMCIA cards. It provides a BIOS-level software interface to the hardware, effectively hiding the specific details from higher levels of software. Socket services also detect when you insert or remove a PCMCIA card and identify the type of card it is.

software: An application program or an operating system that a computer can execute. Software is a broad term that can imply one or many programs, and it can also refer to applications that may actually consist of more than one program.

software driver: Software that acts as the liaison between a piece of hardware and the operating system and allows the use of a component. solenoid An electromechanical device that, when activated, produces an instant push or pull force.

source code: All computer programs-operating system or application-are nothing but a collection of program code. This is the source code or "source" that defines what a program is and how it works. The open source movement is involved with allowing you to check out and even modify this code.

spin speed: An indication of how fast the platters on a fixed disk are spinning.

spindle: The rod that platters are mounted to on in a hard disk drive.

SRAM: check out static RAM (SRAM).

ST506 interface: A popular hard-disk interface standard developed by Seagate Technologies, first used in IBM's PC/XT computer and still popular today, with disk capacities smaller than about 40MB. ST506 has a relatively slow data transfer rate of 5 megabits per second. stack Another name for the memory map, or the way memory is laid out.

standard peripheral power connector: Type of connector used to power various internal drives. Also called a Molex connector.

star network: A network topology in the form of a star. At the center of the star is a wiring hub or concentrator, and the nodes or workstations are arranged around the central point representing the points of the star.

start bit: In asynchronous transmissions, a start bit is transmitted to indicate the beginning of a new data word.

Start menu: As the main focus of the Windows 9x/NT/2000 user interface, the Start menu allows program shortcuts to be placed for easy and organized access.

static RAM (SRAM): A kind of computer memory that retains its contents as long as power is supplied. It does not need constant refreshment like dynamic RAM chips.

static-charge eliminator strip: The device in EP process printers that drains the static charge from the paper after the toner has been transferred to the paper.

stepper motor: A very precise motor that can move in very small increments. Often used in printers.

stop bit(s): In asynchronous transmissions, stop bits are transmitted to indicate the end of the current data word. Depending on the convention in use, one or two stop bits are used.

STP (shield twisted-pair): Cabling that has a braided foil shield around the twisted pairs of wire to decrease electrical interference. stylus A pen-like pointing device used in pen-based systems and personal digital assistants.

subnet mask: The subnet mask is a required part of any TCP/IP configuration, and it is used to define which addresses are local and which are on remote networks.

superscalar: check out parallel processing.

SuperVGA (SVGA): An enhancement to the Video Graphics Array (VGA) video standard defined by the Video Electronics Standards Association (VESA).

surface mount: check out Quad Small Outline Package (QSOP).

surge suppressor: Also known as a surge protector. A regulating device placed between the computer and the AC line connection that protects the computer system from power surges.

SVGA: check out SuperVGA (SVGA).

swap file: On a hard disk, a file used to store parts of running programs that have been swapped out of memory temporarily to make room for other running programs. A swap file may be permanent, always occupying the same amount of hard disk space even though the application that created it may not be running, or is temporary, only created as and when needed.

synchronization: The timing of separate elements or events to occur simultaneously. 1. In a multimedia presentation, synchronization ensures that the audio and video components are timed correctly, so they actually make sense. 2. In computer-to-computer communications, the hardware and software must be synchronized so that file transfers can take place. 3. The process of updating files on both a portable computer and a desktop system so that they both have the latest versions is also known as synchronization.

synchronous DRAM: A kind of DRAM memory module that uses memory chips synchronized to the speed of the processor.

synchronous transmission: In communications, a transmission method that uses a clock signal to regulate data flow. Synchronous transmissions do not use start and stop bits.

syntax: Syntax is a term used to describe the proper way of forming a text command for entry into the computer. Many commands have a number of different options, each of which requires a particular format.

system attribute: Attribute of DOS that is used to tell the OS that this file is needed by the OS and should not be deleted. Marks a file as part of the operating system and will also protect the file from deletion.

system board: The sturdy sheet or board to which all other components on the computer are attached. These components consist of the CPU, underlying circuitry, expansion slots, video components, and RAM slots, just to name a few. Also known as a logic board, motherboard, or planar board.

system disk: A disk that contains all the files necessary to boot and start the operating system. In most computers, the hard disk is the system disk; indeed, many modern operating systems are too large to run from floppy disk.

system.ini: In Microsoft Windows, an initialization file that contains information on your hardware and the internal Windows operating environment.

system resources: On a Windows 3.x or 95/98 machine, the system resources represent those components of the PC that are being used (memory, CPU, etc.). system software The programs that make up the operating system, along with the associated utility programs, as distinct from an application program.

tabs: On many windows you will find that, to save space, a single window will have many tabs, each of which can be selected to display particular information. tape cartridge A self-contained tape storage module, containing tape much like that in a video cassette. Tape cartridges are primarily used to back up hard disk systems.

tape drive: Removable media drive that uses a tape cartridge that has a long polyester ribbon coated with magnetic oxide and wrapped around two spools with a read/write head in between.

target: Another name for the backup media, it is the destination for the data being backed up. It is usually a tape drive or other backup device. taskbar The area of the Windows 9x/NT/2000 interface which includes the Start button and the System Tray, as well as icons for any open programs.

TCP/IP: It stands for Transmission Control Protocol/Internet Protocol. A set of computer-to-computer communications protocols that encompass media access, packet transport, session communications, file transfer, e-mail, and terminal emulation. TCP/IP is supported by a very large number of hardware and software vendors and is available on many different computers from PCs to mainframes.

temporary swap file: A swap file that is created every time it is needed. A temporary swap file will not consist of a single large area of contiguous hard disk space, but may consist of several discontinuous pieces of space. By its very nature, a temporary swap file does not occupy valuable hard disk space if the application that created it is not running. In a permanent swap file the hard disk space is always reserved and is therefore unavailable to any other application program.

terminal: A monitor and keyboard attached to a computer (usually a mainframe), used for data entry and display. Unlike a personal computer, a terminal does not have its own central processing unit or hard disk.

Terminate and Stay Resident (TSR): A DOS program that stays loaded in memory, even when it is not actually running, so that you can invoke it very quickly to perform a specific task.

terminator: A device attached to the last peripheral in a series or the last node on a network. A resistor is placed at both ends of a coax Ethernet cable to prevent signals from reflecting and interfering with the transmission.

text mode: A video display mode for a video card that allows it to only display text. When running DOS programs, a video card is in text mode.

thermal printer: A nonimpact printer that uses a thermal printhead and specially treated paper to create an image.

thick Ethernet: Connecting coaxial cable used on an Ethernet network. The cable is 1 cm (approximately 0.4") thick and can be used to connect network nodes up to a distance of approximately 3300 feet. Thick Ethernet is primarily used for facility-wide installations. Also known as 10Base5.

thin Ethernet: Connecting coaxial cable used on an Ethernet network. The cable is 5 mm (approximately 0.2") thick, and can be used to connect network nodes up to a distance of approximately 1000 feet. Thin Ethernet is primarily used for office installations. Also known as 10Base2.

thrashing: A slang term for the condition that occurs when Windows must constantly swap data between memory and hard disk. The hard disk spins continuously during this and makes a lot of noise.

token passing: A media access method that gives every NIC equal access to the cable. The token is a special packet of data that is passed from computer to computer. Any computer that wants to transmit has to wait until it has the token, at which point it can add its own data to the token and send it on.

Token Ring network: A local area network with a ring structure that uses token-passing to regulate traffic on the network and avoid collisions. On a Token Ring network, the controlling computer generates a "token" that controls the right to transmit. This token is continuously passed from one node to the next around the network. When a node has information to transmit, it captures the token, sets its status to busy, and adds the message and the destination address. All other nodes continuously read the token to determine if they are the recipient of a message; if they are, they collect the token, extract the message, and return the token to the sender. The sender then removes the message and sets the token status to free, indicating that it can be used by the next node in sequence.

tolerance band: Found on a fixed resistor, this colored band indicates how well the resistor holds to its rated value.

toner: Black carbon substance mixed with polyester resins and iron oxide particles. During the EP printing process, toner is first attracted to areas that have been exposed to the laser in laser printers and is later deposited and melted onto the print medium.

toner cartridge: The replaceable cartridge in a laser printer or photocopier that contains the electrically charged ink to be fused to the paper during printing.

topology: A way of laying out a network. Can describe either the logical or physical layout.

touch screen: A special monitor that lets the user make choices by touching icons or graphical buttons on the screen.

Tracert: Used to trace the path of a packet across a TCP/IP network.

trackball: An input device used for pointing, designed as an alternative to the mouse.

tracks: The concentric circle unit of hard disk division. A disk platter is divided into these concentric circles.

transfer corona assembly: The part of an EP process printer that is responsible for transferring the developed image from the EP drum to the paper.

transfer step: The step in the EP print process where the developed toner image on the EP drum is transferred to the print media using the transfer corona.

Transmission Control Protocol/Internet Protocol: check out TCP/IP.

Transport layer: The fourth of seven layers of the International Standards Organization's Open Systems Interconnection (ISO/OSI) model for computerto-computer communications. The Transport layer defines protocols for message structure and supervises the validity of the transmission by performing some error checking.

TSR: check out Terminate and Stay Resident (TSR).

twisted-pair cable: Cable that comprises two insulated wires twisted together at six twists per inch. In twisted-pair cable, one wire carries the signal and the other is grounded. Telephone wire installed in modern buildings is often twistedpair wiring.

UART: It stands for Universal Asynchronous Receiver/Transmitter. An electronic module that combines the transmitting and receiving circuitry needed for asynchronous transmission over a serial line. Asynchronous transmissions use start and stop bits encoded in the data stream to coordinate communications rather than the clock pulse found in synchronous transmissions.

Ultra DMA IDE: Also known as ATA version 4 (ATA-4), it can transfer data at 33Mbps, so it is also commonly seen in motherboard specifications as Ultra DMA/33, Ultra 66, or UDMA.

uninstall: To remove a program from a computer. This generally involves removing its configuration information from the Registry, its icons from the Start menu, and its program code from the file system.

Universal Serial Bus: check out USB.

Unix: Pronounced "you-nix." A 32-bit, multiuser, multitasking, portable operating system.

upper memory area: check out reserved memory area.

upper memory block (UMB): Free areas of memory that can be used for loading drivers and programs into the upper memory area.

USB: It stands for Universal Serial Bus. A technology used to connect peripheral devices to a computer. Each USB channel will support 127 devices and has a total transfer rate of up to 12MBps.

user.exe: Windows core component that allows a user to interact with Windows. It is the component responsible for interpreting keystrokes and mouse movements and sending the appropriate commands to the other core components.

user profiles: In order to allow each user to customize their Windows experience, user profiles save a particular user's desktop appearance and preferences so that when they log on, they will always have there own desktop, even if they share the machine with others.

utility program: A small program or set of small programs that support the operating system by providing additional services that the operating system does not provide.

UTP: It stands for unshielded twisted-pair. A kind of unshielded network cable that contains multiple conductors in pairs that are twisted around each other.

version: Each time that computer software is modified, new features are added and old problems are, hopefully, fixed. To tell these modified programs apart, computer programmers use versions. These are incremented by one digit (for example, from 1.0 to 2.0) for major revisions, or by a tenth of a digit (for example, from 2.0 to 2.1) for minor modifications. Higher version numbers mean newer versions.

VGA: It stands for Video Graphics Array. A video adapter. VGA supports previous graphics standards, and provides several different graphics resolutions, including 640 pixels horizontally by 480 pixels vertically. A maximum of 256 colors can be displayed simultaneously, chosen from a palette of 262,114 colors. Because the VGA standard requires an analog display, it is capable of resolving a continuous range of gray shades or colors. In contrast, a digital display can only resolve a finite range of shades or colors.

video adapter: An expansion board that plugs into the expansion bus in a DOS computer and provides for text and graphics output to the monitor. The adapter converts the text and graphic signals into several instructions for the display that tell it how to draw the graphic.

Video Graphics Array check out VGA.

video RAM (VRAM): Special-purpose RAM with two data paths for access, rather than just one as in conventional RAM. These two paths let a VRAM board manage two functions at once-refreshing the display and communicating with the processor. VRAM doesn't require the system to complete one function before starting the other, so it allows faster operation for the whole video system.

virtual memory: It is a technique of an operating system to enable a process to use a memory (RAM) address space that is independent of other processes running in the same system, and use a space that is larger than the actual amount of RAM present, temporarily sending some contents from RAM to a disk with little or no overhead.

virus: A computer virus is an executable program designed to damage your hard disk contents, and/or interfere normal operation of your computer.

VL bus: Also known as VL local bus. It stands for the VESA local bus, a bus architecture introduced by the Video Electronics Standards Association, VESA, in which up to three adapter slots are built into the motherboard. The VL bus allows for bus mastering.

VLSI (Very Large Scale Integration): Technology used by chip manufacturers to integrate the functions of several small chips into one chip. volts Unit of electrical potential.

VRAM: check out video RAM (VRAM).

wait state: A clock cycle during which no instructions are executed because the processor is waiting for data from a device or from memory.

WAN (wide area network): Network that expands LANs to include networks outside of the local environment.

warm boot: It is a way of rebooting pc by pressing Control+Alt+Delete and it doesn't require the computer to perform all of the hardware and memory checks that a cold boot usually does.

wide area network: check out WAN, wide area network.

window: It is a graphical user interface computer operating system.

Windows 95: Windows 95 is a 32-bit, multitasking, multithreaded operating system capable of running DOS, Windows 3.1, and Windows 95 applications and it supports Plug and Play of the appropriate hardware. It allows long filenames of up to 255 characters while also supporting the DOS 8.3 file-naming conventions.

Windows 98: A new version of Windows 95 operating system with many improvements.

Windows 2000: A line of operating systems developed by Microsoft for use on personal computers, business desktops, laptops, and servers. It is a new version of Windows NT 4.0.

Windows Desktop: check out Desktop.

Windows Installer: It is a new utility used by Microsoft to allow users to customize their application installations more easily.

Windows Internet Name Service (WINS): WINS provides a database for the storage and retrieval of NetBIOS computer names. For adding to and querying the database, aach client must register with the WINS server.

Windows NT: It is a 32-bit multitasking portable operating system developed by Microsoft.

win.ini: a basic INI file that was used in versions of the Microsoft Windows operating environment up to Windows 3.11 to store basic settings at boot time.

WINIPCFG: It is the utility in Windows 9x used to allow you to view your current TCP/IP configuration and request a new IP configuration from a DHCP server.

wizard: Wizard is a utility to walk the user through a particular task.

word: Multiple bytes that are associated together. Or it means that Microsoft Word, a document process software.

workgroup: A group of computers which work together and share the same files and databases within a local area network.

working directory: It is a directory to save their temporary files.

workstation: Any personal computer, other than the server, attached to the network.

World Wide Web (WWW): a global information medium which users can read and write via computers connected to the Internet.

write-protect: To prevent the addition or deletion of files on a disk or tape. A floppy disk has a write-protect notch or small write-protect tab that allow files to be read from the disk, but not modifications or deletions.

write-protect tab: A small notch or tab in a floppy disk used to write-protect data on it.

x86 series: The name for the Intel line of IBM-compatible CPUs.

XGA: It stands for Extended Graphics Array. XGA is only available as a micro channel architecture expansion board; it is not available in ISA or EISA form. XGA supports resolution of 1024 horizontal pixels by 768 vertical pixels with 256 colors, as well as a VGA mode of 640 pixels by 480 pixels with 65,536 colors, and like the 8514/A, XGA is interlaced. XGA is optimized for use with graphical user interfaces, and instead of being very good at drawing lines, it is a bit-block transfer device designed to move blocks of bits like windows or dialog boxes.

zero insertion force (ZIF): A kind of processor socket where you don't need to push the chip into the socket. What you need to do is simply set the chip into the ZIF socket and push a bar down to secure it.

zero wait state: It is a clock cycle during which no instructions are executed because the processor is waiting for data from a device or from memory.

ZIF socket: ZIP stands for Zero Insertion Force. It is a specially designed chip socket to make replacing a chip easier and safer.

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