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Cache An amount of RAM set aside to hold data that is expected to be accessed again. The second access, which finds the data in RAM, is very fast. (Pronounced like "cash.")

Cache controller The microchip on the systemboard that controls the memory cache to static RAM.

Cache memory Also known as cache RAM; a small, high-speed memory device located between the CPU and the system DRAM. Cache is designed to supply the processor with the most frequently requested instructions and data. Cache memory can be three to five times faster than system DRAM.

Call tracking A system that tracks the dates, times, and transactions of help-desk or on-site PC support calls, including the problem presented, the issues addressed, who did what, and when and how each call was resolved.

CAM (Common access method) A standard adapter driver used by SCSI.

Cards Adapter boards or interface cards placed into expansion slots to expand the functions of a computer, allowing it to communicate with external devices such as monitors or printers.

Carrier A reference signal used to activate a phone line to confirm a continuous frequency; used to indicate that two computers are ready to receive or transmit data via modems.

CAU (Controlled-access unit) A centralized hub on a Token Ring network. See Multistation access unit.

CSMA/CD (Carrier Sense Multiple Access with Collision Detection) A feature used in ethernet networks whereby packets are sent after listening for a silence, and are resent if a collision is detected.

Capacity Total amount of user data that can be stored on a device.

CCIA (Computer and Communications Industry Association) A trade association composed of computer and communications firms. It represents their interests in domestic and foreign trade, and keeps members advised of relevant standards and regulatory policy.

CCIR Consultative Committee for International Radio communications.

CGA IBM's first color graphics standard, capable of 320 by 320 resolution at four colors (or gray shades on laptops), or 640 by 200 at two colors (black and white). CGA-only laptops are behind the times.

Chain A group of clusters used to hold a single file.

Checksum A method of error checking of transmitted data, whereby the digits are added up and their sum compared to an expected sum.

Child, parent, grandparent backup method A plan for backing up and reusing tapes or removable disks by rotating them each week (child), month (parent), and year (grandparent).

Chip An integral part of the PC. These are very tiny, square or rectangular slivers of material (usually silicon) with electrical components built in. Some of the chips in a computer aid in memory, but the most important chip is the microprocessor. This is the "8088", "286", "386", or "486" that is referred to when talking about a specific machine's features.

Chip set A set of chips on the systemboard that collectively controls the memory cache, external buses, and some peripherals.

CHKDSK command A DOS command that checks for some hard drive errors and displays possible problems (for example, CHKDSK C: is used to check drive C).

CHS (cylinders, heads, sectors) The traditional method by which BIOS reads and writes to hard drives by addressing the correct cylinder, head, and sector.

Circuit boards Computer components, such as the main systemboard or an adapter board, that have electronic circuits and chips.

Clamping voltage The maximum voltage allowed through a surge suppressor, such as 175 or 330 volts.

Class addresses Class C network addresses a service provider owns and then subleases to small companies.

Clone An IBM PC/XT- or AT-compatible computer made by another manufacturer.

Clock speed The speed at which the CPU operates, a speed of 150MHz, while a Pentium II may operate at 233MHz.

Cluster One or more sectors that constitute the smallest unit of space on a disk for storing data (also referred to as a file allocation unit). Files are written to the disk as groups of whole clusters.

Cluster chain A series of clusters used to hold a single file.

CLV (Constant linear velocity) A CD-ROM format in which the spacing of data is consistent on the CD, but the speed of the disk varies depending on whether the device is reading near the center or the edge of the disc.

CMD files Windows NT batch files that contain a list of commands to be executed as a group.

CMOS (complementary metal oxide semiconductor) chip A type of memory chip that retains its data when power is turned off as long as it retains a trickle of power from a battery.

CNR (Communications and Networking Riser) The CNR specification provides the PC Industry the opportunity to deliver a flexible and cost reduced method of implementing LAN, home networking, DSL, USB, wireless, audio and modem subsystems widely used in today's "connected PCs". The CNR Specification is an open industry specification and is supported by OEMs, IHV card manufacturers, silicon supplier and Microsoft.

COAST (cache on a stick) Chips on a module available for pipelined burst synchronous SRAM.

CODEC (COder/ DEcoder) A method of compressing and later decompressing sound, animation, and video files. MPEG is a common example.

Coding The act of programming a computer; specifically, generating source code in the language of the program's choice. The most popular languages used by programmers are Pascal, C, and C++.

COMDEX (COMputer Dealers Exposition) A twice yearly - once in the spring (in Atlanta) and once in autumn (in Las Vegas) - trade show originally created for computer dealers and distributors but nowadays also attended by large numbers of end users. The first COMDEX in the autumn of 1979 had 157 exhibitors and 4,000 attendees. By the end of the millennium the events were attracting more than 2,000 exhibitors and 200,000 people annually

COM Port A serial port for attaching modem, plotter, printer, or mouse to a system. There are usually 2 COM port connectors: a 9-pin (DB-9) for the mouse, and a 25-pin (DB-25) for a plotter or external modem.

Communications parameters Settings that define how your communications software will handle incoming data and transmit outgoing data. Parameters include bits per second, parity, data bits, and stop bits.

Contention-based system A system in which each computer contends for the opportunity to transmit on the network. If there is a collision, a computer waits a random amount of time and resends.

Controller board An adapter board used to interface the computer and a device such as a scanner.

Convergence A video term that describes the way in which the three beams that generate the three color dots (red, green, blue) should meet. When all three dots are excited at the same time and their relative distance is perfect, the result is pure white. Deviation from this harmony (due to an incorrect relationship of the beams to each other) results in poor convergence. This causes white pixels to show bits of color and can decrease image sharpness and resolution.

Continuity A continuous, unbroken path for the flow of electricity. A "continuity test" can determine whether or not internal wiring is still intact.

Collision In an ethernet network, when transmitted packets of data are sent at the same time and collide. Ethernet will first listen for silence before it transmits, and it will stop and resends if a collision occurs.

Color depth The number of possible colors used by the monitor. Determines the number of bits used to compose one pixel. One of two characteristics (the other is screen resolution) that determine the amount of data sent to the video card to build one screen.

Color depth The number of possible colors used by the monitor. Determines the number of bits used to compose one pixel. One of two characteristics (the other is screen resolution) that determine the amount of data sent to the video card to build one screen.

Color space conversion Converting images to RGB values before they are displayed. Processing is faster if the video card does the conversion instead of the CPU.

Compressed drive A drive whose format has been reorganized, in order to store more data. A compressed drive is really not a drive at all; it's actually a type of file, typically with a host drive called H.

CompTIA (Computing Technology Industry Association) A membership trade association that sponsors A+ Certification, a valuable certification for PC technician.

Comment lines Documentation lines that are ignored by the OS or software executing a list of instructions. A REM in front of a line will turn an AUTOEXEC.BAT command into a comment. A semicolon will turn an .ini file line into a comment.

Configuration data Also called setup information. Information about the computer's hardware, such as what type of hard drive, floppy drive, or monitor is present, along with other detailed settings.

Configuration manager A component of Windows 95 Plug-and-Play that controls the configuration process of all devices and communicates these configurations to the devices.

Configuration parameter Another name for the value names and values of the registry, which is information in the Windows registry.

Control blade A laser printer component that prevents too much toner from sticking to the cylinder surface.

Connection protocol In networking, confirming that a good connection is made before transmitting data to the other end. To accomplish this, most network applications use TCP rather than UDP.

Connectionless protocol When UDP is used and a connection is not required before sending a packet. Consequently, there is no guarantee that the packet will arrive at its destination. An example of a UDP transmission is a broadcast to all nodes on a network.

Coprocessor A chip or portion of the CPU that helps the microprocessor perform calculations and speeds up computation and data manipulations dramatically.

Copy backup A full backup that does not change the archive attributes of files and folders, so that incremental and differential backups don't "sense" this backup.

COPY command A DOS command that copies files from one location to another (for example, COPY FILE.EXT A: is used to copy the file named FILE.EXT to the disk in drive A).

Corrupted files Data and program files that are damaged for any of a variety of reasons, ranging from power spikes to user error.

CPU (Central Processing Unit) Also called a microprocessor. The heart and brain of the computer, which receives data input, processes the information, and executes instructions.

Credit card memory A type of memory typically used in laptop and notebook computers. Credit card memory features a small for factor and named for it’s similarity to size of credit card.

Crosstalk The interference that one wire, in a twisted pair, may produce in the other.

Cross-linked clusters Errors caused when files appear to share the same disk space, according to the file allocation table.