Z39.50 standard

n. A specification for a query language based on SQL (structured query language). It is used by WAIS, among other Internet services, to search for files through the use of keywords and is widely used for remote access to library catalogs. See also structured query language, WAIS.

ZD Net

n. A Web site designed for PC users that hosts a wide range of technical special interest groups (SIGs), as well as freeware and shareware utilities. It was founded by the Ziff Davis publishing group as an online information service. Also called ZiffNet. See also SIG.

zepto-

prefix A metric prefix meaning 10^-21 (one sextillionth in the American system).

zero¹

n. The arithmetic symbol (0) representing no magnitude.

zero²

vb. To fill or replace with zeros (for example, to zero a specified portion of memory, a field, or some other limited structure).

zero-insertion-force socket

n. See ZIF socket.

zero out

vb. To set a variable value or a series of bits to zero.

zetta-

prefix A metric prefix meaning 10²¹ (one sextillion in the American system).

ZIF socket

n. Short for zero-insertion-force socket. A kind of socket for integrated circuits that can be opened with a lever or screw, allowing the chip to be placed in the socket without the application of pressure. The lever or screw of the socket is then closed, causing the socket contacts to grip the chip's pins. ZIF sockets facilitate frequent insertion and removal of chips, but they take up more space and are more expensive than conventional sockets.

Zip drive

n. A disk drive developed by Iomega that uses 3.5-inch removable disks (Zip disks) capable of storing 100 megabytes of data. See also disk drive.

Zmodem

n. An enhancement of the Xmodem file transfer protocol that handles larger data transfers with less error. Zmodem includes a feature called checkpoint restart, which resumes transmission at the point of interruption, rather than at the beginning, if the communications link is broken during data transfer. See also Xmodem.

zoom

vb. To enlarge a selected portion of a graphical image or document to fill a window or the screen. Zooming is a feature of many programs, including drawing, word processing, and spreadsheet programs, that allow the user to select a small part of the screen, zoom it, and make changes to the enlarged portion at a finer level of detail. See also window.

Zulu time