240 Glossary

Terms

CPU — See central processing unit (CPU).

CPU cache — A section of very fast memory residing between the CPU and the computer’s main memory that temporarily stores data and instructions the CPU will need to execute commands and programs. See also cache, L1 cache, L2 cache.

cursor — A symbol that indicates the current position on the screen. The shape of the cursor varies, depending on the program you’re using and what you’re doing.

D

default — The setting selected by a program when the user does not

 

 

specify an alternative setting.

 

device — A component attached to the computer. Devices may be

 

external (outside the computer’s case) or internal (inside the

 

computer’s case). Printers, disk drives, and modems are examples of

 

devices.

 

device driver — A program (called a “driver”) that permits a computer

 

to communicate with a device.

 

dialog box — An on-screen window displayed by the operating system

 

or a program giving a direction or requesting input from the user.

 

direct current (DC) — The type of power usually supplied by batteries.

 

DC flows in one direction. Compare alternating current (AC).

 

direct memory access (DMA) — A dedicated channel, bypassing the

 

CPU, that enables direct data transfer between memory and a device.

 

directory — See folder.

 

disable — To turn a computer option off. See also enable.

 

disc — A round, flat piece of metal, designed to be read from and written

 

to by optical (laser) technology, and used in the production of optical

 

discs, such as CDs and DVDs. Compare disk.

 

disk — A round, flat piece of material that can be magnetically

 

influenced to hold information in digital form, and used in the

 

production of magnetic disks, such as diskettes and hard disks.

 

Compare disc. See also diskette, hard disk.

 

disk drive — The device that reads and writes information and programs

 

on a diskette or hard disk. It rotates the disk at high speed past one or

 

more read/write heads.