204 Glossary

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 material, 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.

diskette — A thin, flexible disk in a protective jacket that stores magnetically encoded data. Diskettes can be removed from the computer and come in two sizes: 5.25-inch and 3.5-inch. Your computer uses 3.5-inch diskettes. See also double-density diskette, high-density diskette.

document — Any file created with an application and, if saved to disk, given a name by which it can be retrieved. See also file.

double-click— To press and release the pointing device’s primary button rapidly twice without moving the pointing device. In the Windows® operating system, this refers to the pointing device’s left button, unless otherwise stated.