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222 Glossary<br />
D<br />
cursor — An on-screen symbol (usually a flashing vertical line) that<br />
indicates the position where characters will appear when you enter<br />
data.<br />
default — The setting selected by a program when the user does not<br />
specify an alternative setting.<br />
device — A component attached to the computer. Devices may be<br />
external (outside the computer’s case) or internal (inside the<br />
computer’s case). Printers, disk drives, and modems are examples of<br />
devices.<br />
device driver — A program (called a “driver”) that permits a computer<br />
to communicate with a device.<br />
dialog box — An on-screen window displayed by the operating system<br />
or a program giving a direction or requesting input from the user.<br />
direct current (DC) — The type of power usually supplied by batteries.<br />
DC flows in one direction. Compare alternating current (AC).<br />
direct memory access (DMA) — A dedicated channel, bypassing the<br />
CPU, that enables direct data transfer between memory and a<br />
device.<br />
directory — See folder.<br />
disable — To turn a computer option off. See also enable.<br />
disc — A round, flat piece of material, designed to be read from and<br />
written to by optical (laser) technology, and used in the production<br />
of optical discs, such as CDs and DVDs. Compare disk.<br />
disk — A round, flat piece of material that can be magnetically<br />
influenced to hold information in digital form, and used in the<br />
production of magnetic disks, such as diskettes and hard disks.<br />
Compare disc. See also diskette, hard disk.<br />
disk drive — The device that reads and writes information and programs<br />
on a diskette or hard disk. It rotates the disk at high speed past one or<br />
more read/write heads.<br />
diskette — A thin, flexible disk in a protective jacket that stores<br />
magnetically encoded data. Diskettes can be removed from the<br />
computer and come in two sizes: 5.25-inch and 3.5-inch. Your<br />
computer uses 3.5-inch diskettes. See also double-density diskette,<br />
high-density diskette.