IEEE Std 610.10-1994
`
`IEEE Standard Glossary of
`Computer Hardware Terminology
`
`Sponsor
`Standards Coordinating Committee
`of the
`
`IEEE Computer Society
`
`Approved June 14, 1994
`
`IEEE Standards Board
`
`written permission of the publisher.
`
`re defined. Terms falling under the categories
`Abstract: Terms pertaining to computer hard
`of computer architecture, computer storage, generalhardWare concepts, peripherals, and proces-
`sors and components are included.
`'
`Keywords: computer, hardware, definition, glossary, terminology
`
`This standard is one of a number of information technology dictionaries developed by standards organizations accred-
`ited by the American National Standards Institute. These dictionaries are developed under the sponsorship of vol untary
`standards organizations, using a consensus-based process.
`
`The Instituteof Electrical and Electronics Engineers, inc.
`345 East 47th Street, New York, NY 10017-2394, USA
`
`Copyright © 1995 by the Institute of Electrical and Electronics Engineers. Inc.
`All rights reserved. Published 1995. Printed in the United States of America.
`ISBN 1-55937—492-6
`
`No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior
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`COMPUTER HARDWARE TERMINOLOGY
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`3.1677 pointer. (1) A data item that specifies the loca-
`tion of another data item; for example, a data item that
`specifies the address of the next employee record to be
`processed. [IEEE Std 610.12—1990] (2) An identifier that
`indicates the address or storage location of a data item.
`
`3.1678 pointing device. An input device that is used to
`specify a particular addressable location. See also: cur-
`sor control device; stylus. Contrast with: pick device.
`[IEEE Std 610.6—1991]
`
`3.1679 polarity. The orientation of any device that has
`poles or signed electrodes.
`
`3.1680 polarized dipole magnetization. See: polarized
`return-to-zero recording.
`
`3.1681 polarized return-to-zero recording (RZ(P))._
`Return-to-zero recording in which zeros are represented
`by magnetization in one sense, ones are represented by
`magnetization in the opposite sense, and the reference
`condition is the absence of magnetization. Syn: polar-
`ized dipole magnetization. Contrast with: non—polarized
`return-to-zero recording.
`'
`
`3.1682 port. An input or output COnnection between a
`peripheral device and a computer. See also: input-output
`port; mouse port; parallel port; serial port.
`-
`
`3.1683 portable computer. A personal computer that is
`designed and configured to permit transportation as a
`piece of handheld luggage. Note: US. Federal regula—
`tions limit use of the term “portable” to objects weigh—
`ing no more than 21 pounds. See also: hand—held
`computer; laptop computer; notebook computer; trans-
`portable computer. [IEEE Std 610.2-1987]
`
`3.1684 portrait orientation. A page orientation of a
`display surface having greater height than width. Note:
`Derived from portraits of people, which are usually ver-
`tical in format. Contrast with: landscape orientation.
`
`3.1685 position. See: seek.
`
`3.1687 positioning time. See: seek time.
`
`instruction and the availability of the next.
`
`3.1686 positional servomechanism. In an analog com-
`puter, a servomechanism in which a mechanical shaft is
`positioned, usually in the angle of rotation, in accor-
`dance with one or more input signals. Note: Frequently,
`the shaft is positioned (excluding transient motion) in a
`manner linearly related to the value of the input signal.
`See also: repeater servomechanism, servomechanism.
`
`lEEE
`Std 610.10-1994
`
`3.1688 positive. Pertaining to a voltage or charge that is
`associated with a deficiency of electrons. Contrast with:
`negative.
`
`3.1689 postamble. A sequence of bits recorded at the
`end of each block on a magnetic medium for the pur—
`pose of synchronization when reading backward. Con-
`trast with: preamble. [ANSI X3.l38-l988]
`
`3.1690 potentiometer. A resistor with an adjustable
`sliding contact that functions as an adjustable voltage
`divider. See also: function potentiometer; parameter
`potentiometer; servo potentiometer.
`
`3.1691 potentiometer set. In an analog computer, a
`computer—control state that supplies the same operating
`potentiometer loading as under computing conditions
`and thus allows correct potentiometer adjustment.
`
`3.1692 power supply. A unit that converts voltage from
`one level to another, usually regulating the output. Note:
`.E Typically used to convert an AC voltage to a DC volt-
`age. See also: converter.
`
`3.1693 power-fail circuit. A logic circuit that protects
`an operating program if primary power fails by inform-
`ing the computer when power failure is imminent, initi—
`ating a routine that saves all volatile data. After power
`has been restored,
`the circuit initiates a routine that
`restores the data and restarts computer operations.
`
`3.1694 pre-read head. A read head that is placed before
`another read head and is used to read data before the
`
`same data are read by the other read head.
`
`3.1695 preamble. A sequence of bits recorded at the
`beginning of each block on a magnetic tape for the pur-
`pose of synchronization. Contrast with: postamble.
`[ANSI X3.138-1988]
`
`3.1696 precision. The degree of exactness or discrimi-
`nation with which a quantity is stated. Note: The result
`of a calculation may have more precision than it has
`accuracy; for example, the true value of pi to six signifi-
`cant digits is 3.14159; the value of 3.14162 is precise to
`six digits but only five digits are accurate. See also:
`accuracy. [IEEE Std 610.12-1990a]
`
`3.1697 prefetching. In a pipelined process, to fetch the
`next instruction, or instruction part, before the process—
`ing unit requires it, resulting in a performance improve-
`ment by eliminating the lag between completion of one
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