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z-buffer or z-buffering. In 3D computer graphics, applies both to the device and the techniques commonly used as an aid in removing hidden lines and hidden surfaces. If z-buffering is enabled, each pixel stores a depth value as well as a color value. In simple terms, the depth can be thought of as the distance from the viewer's eye to the pixel. Whenever a drawing routine tries to update a pixel, it first checks the current pixel's "depth" or "z-value" and will only update that pixel with new values if the new pixel is closer than the current pixel. The region of memory that stores the z-values is also referred to as the z-buffer. See also hidden surface.

Z format. The format of a pixmap organized as a set of pixel values in scanline order. See also XY format.

zero bit insertion and deletion. Inserting a zero after every four 1-bits and then removing the zeros to return the data to normal.

zero suppression. The removal or substitution of blanks for leading zeros in a number. For example, 00057 becomes 57 when using zero suppression.

zombie process. An ended process whose entry remains in the process table, but to which a user or kernel space is not allocated. A process becomes a zombie process when it issues the exit subroutine and the following circumstances occur: Its parent process is not running a wait subroutine and has not set its SIGCLD signal action to the SIG_IGN value indicating that it does not intend to wait for its children to finish.

zone of authority. The set of names managed by a single name server.

zoom factor. A multiplier to determine the amount of enlargement of a specified screen rectangle. The x zoom factor determines the enlargement in the x direction; the y zoom factor determines the enlargement in the y direction.

zooming. In computer graphics, the progressive scaling of a display image to give the visual impression of going from a faraway view of an image to a close-up view, or a close-up view to a faraway view.

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