P5
n. Intel Corporation's internal working name for the Pentium microprocessor.
Although it was not intended to be used publicly, the name P5 leaked out to the
computer-industry trade press and was commonly used to reference the microprocessor before
it was released. See also 586, Pentium.
packet
n. 1. A unit of information transmitted as a whole from one device to another on
a network. 2. In packet-switching networks, a transmission unit of fixed maximum size that
consists of binary digits representing both data and a header containing an identification
number, source and destination addresses, and sometimes error-control data. See also
packet switching.
packet assembler/disassembler
n. An interface between non-packet-switching equipment and a packet-switching
network. Acronym: PAD.
Packet Internet Groper
n. See ping1 (definition 1).
packet switching
n. A message-delivery technique in which small units of information (packets)
are relayed through stations in a computer network along the best route available between
the source and the destination. A packet-switching network handles information in small
units, breaking long messages into multiple packets before routing. Although each packet
may travel along a different path, and the packets composing a message may arrive at
different times or out of sequence, the receiving computer reassembles the original
message. Packet-switching networks are considered to be fast and efficient. To manage the
tasks of routing traffic and assembling/disassembling packets, such a network requires
some "intelligence" from the computers and software that control delivery. The
Internet is an example of a packet-switching network. Standards for packet switching on
networks are documented in the CCITT recommendation X.25.
PAD
n. See packet assembler/disassembler.
page
n. 1. In word processing, the text and display elements to be printed on one
side of a sheet of paper, subject to formatting specifications such as depth, margin size,
and number of columns. 2. A fixed-size block of memory. When used in the context of a
paging memory system, a page is a block of memory whose physical address can be changed
via mapping hardware. See also EMS, memory management unit, virtual memory. 3. In
computer graphics, a portion of display memory that contains one complete full-screen
image; the internal representation of a screenful of information.
page break
n. The point at which the flow of text in a document moves to the top of a new
page. Most word processors automatically place page breaks when the material on the page
reaches a specified maximum. By contrast, a "hard" or "manual" page
break is a command or code inserted by the user to force a page break at a specific place
in the text. See also form feed.
paged address
n. In the 80386, i486, and Pentium paged-memory architecture, an address in
memory created by combining the process of segment translation and page translation. In
the paged-memory scheme, which requires that the microprocessor's paging feature be
enabled, logical addresses are transformed into physical addresses in two steps: segment
translation and page translation. The first step, segment translation, converts a logical
to a linear address--an address that refers indirectly to a physical address. After the
linear address is obtained, the microprocessor's paging hardware converts the linear
address to a physical address by specifying a page table (an array of 32-bit page
specifiers), a page (a 4-KB unit of contiguous addresses within physical memory) within
that table, and an offset within that page. This information collectively refers to a
physical address.
Page Down key
n. A standard key (often labeled "PgDn") on most computer keyboards
whose specific meaning is different in different programs. In many cases, it moves the
cursor down to the top of the next page or a specific number of lines.
page fault
n. The interrupt that occurs when software attempts to read from or write to a
virtual memory location that is marked "not present." The mapping hardware of a
virtual memory system maintains status information about every page in the virtual address
space. A page either is mapped onto a physical address or is not present in physical
memory. When a read or write to an unmapped virtual address is detected, the memory
management hardware generates the page fault interrupt. The operating system must respond
to the page fault by swapping in the data for the page and updating the status information
in the memory management unit. See also page (definition 2), swap (definition 2),
virtual memory.
page layout
n. In desktop publishing, the process of arranging text and graphics on the
pages of a document. Page-layout programs excel in text placement and management of
special effects applied to text. Although page-layout programs are generally slower than
word-processing programs, they can perform such advanced tasks as flowing text into
complex multicolumn page designs, printing documents in signatures, managing color
separations, and supporting sophisticated kerning and hyphenation.
page makeup
n. The assembling of graphics and text on a page in preparation for printing.
Page Up key
n. A standard key (often labeled "PgUp") on most computer keyboards
whose specific meaning is different in different programs. In many cases, it moves the
cursor up to the top of the previous page or a specific number of lines.
paging
n. A technique for implementing virtual memory. The virtual address space is
divided into a number of fixed-size blocks called pages, each of which can be mapped onto
any of the physical addresses available on the system. Special memory management hardware
(MMU or PMMU) performs the address translation from virtual addresses to physical
addresses. See also memory management unit, paged memory management unit, virtual
memory.
paint1
n. A color and pattern used with graphics programs to fill areas of a drawing,
applied with tools such as a paintbrush or a spraycan.
paint2
vb. To fill a portion of a drawing with paint.
paintbrush
n. An artist's tool in a paint program or another graphics application for
applying a streak of solid color to an image. The user can usually select the width of the
streak. See also paint program. Compare spraycan.
palmtop
n. A portable personal computer whose size enables it to be held in one hand
while it is operated with the other hand. A major difference between palmtop computers and
laptop computers is that palmtops are usually powered by off-the-shelf batteries such as
AA cells. Palmtop computers typically do not have disk drives; rather, their programs are
stored in ROM and are loaded into RAM when they are switched on. More recent palmtop
computers are equipped with PCMCIA slots to provide wider flexibility and greater
capability. See also handheld PC, PCMCIA slot, portable computer. Compare
laptop.
Pantone Matching System
n. In graphic arts and printing, a standard system of ink color specification
consisting of a swatch book in which each of about 500 colors is assigned a number. See
also color model. Acronym: PMS.
PAP
n. 1. Acronym for Password Authentication Protocol. A method for verifying the
identity of a user attempting to log on to a Point-to-Point Protocol (PPP) server. PAP is
used if a more rigorous method, such as the Challenge Handshake Authentication Protocol
(CHAP), is not available or if the user name and password that the user submitted to PAP
must be sent to another program without encryption. 2. Acronym for Printer Access
Protocol. The protocol in AppleTalk networks that governs communication between computers
and printers.
paper feed
n. A mechanism that moves paper through a printer. In laser printers and other
page printers, the paper feed is usually a series of rollers that firmly grip and align
the paper. In dot-matrix printers, the paper feed is usually a pin feed or tractor feed,
in which small pins drag or push paper that has detachable edges punched with sprocket
holes. Friction feed is another type of paper feed, in which the paper is gripped between
the platen and pressure rollers and pulled by rotation of the platen.
paperless office
n. The idealized office in which information is entirely stored, manipulated,
and transferred electronically rather than on paper.
paradigm
n. An archetypical example or pattern that provides a model for a process or
system.
paragraph
n. 1. In word processing, any part of a document preceded by one paragraph mark
and ending with another. To the program, a paragraph represents a unit of information that
can be selected as a whole or given formatting distinct from the surrounding paragraphs.
2. On IBM and other computers built around the Intel 8088 or 8086 microprocessor, a
16-byte section of memory beginning at a location (address) that can be divided evenly by
16 (hexadecimal 10).
parallel
adj. 1. Of or relating to electronic circuits in which the corresponding
terminals of two or more components are connected. 2. In geometry and graphics, of,
relating to, or being lines that run side by side in the same direction in the same plane
without intersecting. 3. In data communications, of, relating to, or being information
that is sent in groups of bits over multiple wires, one wire for each bit in a group. See
also parallel interface. Compare serial. 4. In data handling, of or relating to
handling more than one event at a time, with each event having its own portion of the
system's resources. See also parallel processing.
parallel computing
n. The use of multiple computers or processors to solve a problem or perform a
function. See also array processor, massively parallel processing, pipeline
processing, SMP.
parallel port
n. The input/output connector for a parallel interface device. See also
input/output port.
parallel printer
n. A printer that is connected to the computer via a parallel interface. In
general, a parallel connection can move data between devices faster than a serial
connection can. The parallel interface is preferred in the IBM PC world because its
cabling is more standardized than that of the serial interface and because the MS-DOS
operating system assumes that the system printer is attached to the parallel port. See
also parallel interface. Compare serial printer.
parallel server
n. A computer system that implements some form of parallel processing to improve
its performance as a server. See also SMP server.
parallel transmission
n. The simultaneous transmission of a group of bits over separate wires. With
microcomputers, parallel transmission refers to the transmission of 1 byte (8 bits). The
standard connection for parallel transmission is known as the Centronics interface. See
also Centronics parallel interface. Compare serial transmission.
parameter
n. In programming, a value that is given to a variable, either at the beginning
of an operation or before an expression is evaluated by a program. Until the operation is
completed, a parameter is effectively treated as a constant value by the program. A
parameter can be text, a number, or an argument name assigned to a value that is passed
from one routine to another. Parameters are used as a means of customizing program
operation. See also argument, pass by address, pass by value, routine.
PARC
n. See Xerox PARC.
parity
n. The quality of sameness or equivalence, in the case of computers usually
referring to an error-checking procedure in which the number of 1s must always be the
same--either even or odd--for each group of bits transmitted without error. If parity is
checked on a per-character basis, the method is called vertical redundancy checking, or
VRC; if checked on a block-by-block basis, the method is called longitudinal redundancy
checking, or LRC. In typical modem-to-modem communications, parity is one of the
parameters that must be agreed upon by sending and receiving parties before transmission
can take place. Types of parity are shown in the following table. See also parity
bit, parity check, parity error. k:\compdict\database\2297.doc
parity bit
n. An extra bit used in checking for errors in groups of data bits transferred
within or between computer systems. With microcomputers, the term is frequently
encountered in modem-to-modem communications, in which a parity bit is often used to check
the accuracy with which each character is transmitted, and in RAM, where a parity bit is
often used to check the accuracy with which each byte is stored.
parity check
n. The use of parity to check the accuracy of transmitted data. See also
parity, parity bit.
parity error
n. An error in parity that indicates an error in transmitted data or in data
stored in memory. If a parity error occurs in communications, all or part of a message
must be retransmitted; if a parity error occurs in RAM, the computer usually halts. See
also parity, parity bit.
park
vb. To position the read/write head over a portion of a disk that stores no data
(and therefore can never be damaged) or beyond the surface of the disk, prior to shutting
down the drive, especially in preparation for moving it. Parking can be performed
manually, automatically, or, most typically, by a disk utility program.
parse
vb. To break input into smaller chunks so that a program can act upon the
information.
partition
n. 1. A logically distinct portion of memory or a storage device that functions
as though it were a physically separate unit. 2. In database programming, a subset of a
database table or file.
Pascal
n. A concise procedural language designed between 1967 and 1971 by Niklaus
Wirth. Pascal, a compiled, structured language built upon ALGOL, simplifies syntax while
adding data types and structures such as subranges, enumerated data types, files, records,
and sets. See also ALGOL, compiled language. Compare C.
password
n. A security measure used to restrict access to computer systems and sensitive
files. A password is a unique string of characters that a user types in as an
identification code. The system compares the code against a stored list of authorized
passwords and users. If the code is legitimate, the system allows the user access at
whatever security level has been approved for the owner of the password.
Password Authentication Protocol
n. See PAP (definition 1).
password protection
n. The use of passwords as a means of allowing only authorized users access to a
computer system or its files.
paste
vb. To insert text or a graphic that has been cut or copied from one document
into a different location in the same or a different document. See also cut, cut
and paste.
patch1
n. A piece of object code that is inserted in an executable program as a
temporary fix of a bug.
patch2
vb. In programming, to repair a deficiency in the functionality of an existing
routine or program, generally in response to an unforeseen need or set of operating
circumstances. Patching is a common means of adding a feature or a function to a program
until the next version of the software is released. Compare hack (definition 2),
kludge (definition 2).
path
n. 1. In communications, a link between two nodes in a network. 2. A route
through a structured collection of information, as in a database, a program, or files
stored on disk. 3. In programming, the sequence of instructions a computer carries out in
executing a routine. 4. In information processing, such as the theory underlying expert
(deductive) systems, a logical course through the branches of a tree of inferences leading
to a conclusion. 5. In file storage, the route followed by the operating system through
the directories in finding, sorting, and retrieving files on a disk. 6. In graphics, an
accumulation of line segments or curves to be filled or drawn.
pattern recognition
n. 1. A broad technology describing the ability of a computer to identify
patterns. The term usually refers to computer recognition of visual images or sound
patterns that have been converted to arrays of numbers. 2. The recognition of purely
mathematical or textual patterns.
Pause key
n. 1. A key on a keyboard that temporarily stops the operation of a program or a
command. The Pause key is used, for example, to halt scrolling so that a multiscreen
listing or document can be read. 2. Any key that creates a pause in an operation. For
example, many game programs have a Pause key, often simply the P key, that temporarily
suspends the game.
PBX
n. Acronym for Private Branch Exchange. An automatic telephone switching system
that enables users within an organization to place calls to each other without going
through the public telephone network. Users can also place calls to outside numbers.
PC
n. 1. A microcomputer that conforms to the standard developed by IBM for
personal computers, which uses a microprocessor in the Intel 80x86 family (or compatible)
and can execute the BIOS. See also 8086, BIOS, clone, IBM PC. 2. A computer in
IBM's Personal Computer line. Also called IBM PC. See also PC-compatible
(definition 1). See personal computer.
PC Card
n. A trademark of the Personal Computer Memory Card International Association
(PCMCIA) that is used to describe add-in cards that conform to the PCMCIA specification. A
PC Card is a removable device, approximately the same size as a credit card, that is
designed to plug into a PCMCIA slot. Release 1 of the PCMCIA specification, introduced in
June 1990, specified a Type I card that is 3.3 millimeters thick and is intended to be
used primarily as a memory-related peripheral. Release 2 of the PCMCIA specification,
introduced in September 1991, specifies both a 5-millimeter-thick Type II card and a
10.5-millimeter-thick Type III card. Type II cards accommodate devices such as modem, fax,
and network cards. Type III cards accommodate devices that require more space, such as
wireless communications devices and rotating storage media (such as hard disks). See
also PCMCIA, PCMCIA slot.
PC-compatible
adj. Conforming to IBM PC/XT and PC/AT hardware and software specifications,
which has been the de facto standard in the computing industry for personal computers that
use the Intel 80x86 family or compatible chips. Most PC-compatible computers today are
developed outside of IBM; they are still sometimes referred to as clones. Also called
IBM PC. See also 8086, clone, de facto standard, IBM AT. See Wintel.
PC-DOS
n. Acronym for Personal Computer Disk Operating System. The version of MS-DOS
sold by IBM. MS-DOS and PC-DOS are virtually identical, although filenames of utility
programs sometimes differ in the two versions. See also MS-DOS.
PCI local bus
n. Short for Peripheral Component Interconnect local bus. A specification
introduced by Intel Corporation that defines a local bus system that allows up to 10
PCI-compliant expansion cards to be installed in the computer. A PCI local bus system
requires the presence of a PCI controller card, which must be installed in one of the
PCI-compliant slots. Optionally, an expansion bus controller for the system's ISA, EISA,
or Micro Channel Architecture slots can be installed as well, providing increased
synchronization over all the system's bus-installed resources. The PCI controller can
exchange data with the system's CPU either 32 bits or 64 bits at a time, depending on the
implementation, and it allows intelligent, PCI-compliant adapters to perform tasks
concurrently with the CPU using a technique called bus mastering. The PCI specification
allows for multiplexing, a technique that permits more than one electrical signal to be
present on the bus at one time. See also local bus. Compare VL bus.
PCL
n. See Printer Control Language.
PCMCIA
n. Acronym for Personal Computer Memory Card International Association. A group
of manufacturers and vendors formed to promote a common standard for PC Card-based
peripherals and the slot designed to hold them, primarily on laptop, palmtop, and other
portable computers, as well as for intelligent electronic devices. PCMCIA is also the name
of the standard for PC Cards, first introduced in 1990 as release 1. See also PC
Card, PCMCIA slot.
PCMCIA connector
n. The 68-pin female connector inside a PCMCIA slot designed to hold the 68-pin
male connector on a PC Card. See also PC Card, PCMCIA slot.
PCMCIA slot
n. An opening in the housing of a computer, peripheral, or other intelligent
electronic device designed to hold a PC Card. Also called PC Card slot. See also
PC Card, PCMCIA connector.
PC memory card
n. 1. An add-in circuit card that increases the amount of RAM in a system. See
also memory card. 2. A Type I PC Card as specified by PCMCIA. In this context, such a
card consists of conventional static RAM chips powered by a small battery and is designed
to provide additional RAM to the system. See also PC Card. Compare flash
memory.
PCX
n. A graphical file format that compresses its image data with RLE-type
compression, used by early versions of Windows Paintbrush.
PC/XT
n. The original IBM Personal Computer, introduced in 1981, which used the Intel
8088 CPU. See also IBM PC.
PC/XT keyboard
n. The original keyboard for the IBM Personal Computer. Strong, reliable, and
equipped with 83 keys, the PC/XT keyboard offers a typist an audible click. See also
IBM PC, PC/XT.
PDA
n. Acronym for Personal Digital Assistant. A lightweight palmtop computer
designed to provide specific functions like personal organization (calendar, note taking,
database, calculator, and so on) as well as communications. More advanced models also
offer multimedia features. Many PDA devices rely on a pen or other pointing device for
input instead of a keyboard or mouse, although some offer a keyboard too small for touch
typing to use in conjunction with a pen or pointing device. For data storage, a PDA relies
on flash memory instead of power-hungry disk drives. See also firmware, flash
memory, PC Card, pen computer.
PDC
n. See Primary Domain Controller.
PDF
n. See Portable Document Format.
PDL
n. See page-description language.
PDM
n. See pulse duration modulation.
PDO
n. See Portable Distributed Objects.
peer
n. Any of the devices on a layered communications network that operate on the
same protocol level. See also network architecture.
peer-to-peer architecture
n. A network of two or more computers that use the same program or type of
program to communicate and share data. Each computer, or peer, is considered equal
in terms of responsibilities and each acts as a server to the others in the network.
Unlike a client/server architecture, a dedicated file server is not required. However,
network performance is generally not as good as under client/server, especially under
heavy loads. Also called peer-to-peer network. See also peer, peer-to-peer
communications, server. Compare client/server architecture.
peer-to-peer communications
n. Interaction between devices that operate on the same communications level on
a network based on a layered architecture. See also network architecture.
pel
n. Short for picture element. See pixel.
Pentium
n. A microprocessor introduced by Intel Corporation in March 1993 as the
successor to the i486. The Pentium is a superscalar, CISC-based microprocessor containing
3.3 million transistors. The Pentium has a 32-bit address bus, a 64-bit data bus, a
built-in floating-point unit and memory management unit, two built-in 8-KB L1 caches, and
a System Management Mode (SMM), which provides the microprocessor with the ability to slow
or halt some system components when the system is idle or performing non-CPU-intensive
tasks, thereby lessening power consumption. The Pentium also employs branch prediction,
resulting in faster system performance. In addition, the Pentium has some built-in
features to ensure data integrity, and it supports functional redundancy checking (FRC). See
also branch prediction, CISC, functional redundancy checking, i486DX, L1 cache,
microprocessor, P5, superscalar. Compare Pentium Pro (definition 1).
Pentium Pro
n. 1. Intel's 150-200 MHz family of 32-bit processors, released in November
1995. The Pentium Pro is considered the next generation of processors in the 8086 family,
following the Pentium, and is designed for running 32-bit operating systems and
applications. See also 32-bit application, 32-bit operating system, 8086,
microprocessor, Pentium. 2. A PC that has a Pentium Pro processor.
Pentium upgradable
n. 1. An i486 motherboard capable of being adapted to run a Pentium-class
processor. See also i486DX, microprocessor, motherboard, Pentium. 2. A 486 PC that
can be upgraded to Pentium class by adding a Pentium processor. See also i486DX.
performance monitor
n. A process or program that appraises and records status information about
various system devices and other processes.
period
n. The length of time required for an oscillation to complete one full cycle.
For an oscillation electrical signal, the period is the time between waveform repetitions.
If f is the frequency of oscillation in hertz, and t is the period in
seconds, then t = 1/f.
peripheral
n. In computing, a device, such as a disk drive, printer, modem, or joystick,
that is connected to a computer and is controlled by the computer's microprocessor. Also
called peripheral device. See also console.
peripheral power supply
n. An auxiliary source of electricity used by a computer or a device as a backup
in case of a power failure. Acronym: PPS.
Perl
n. Acronym for Practical Extraction and Report Language. An interpreted
language, based on C and several UNIX utilities. Perl has powerful string-handling
features for extracting information from text files. Perl can assemble a string and send
it to the shell as a command; hence, it is often used for system administration tasks. A
program in Perl is known as a script. Perl was devised by Larry Wall at NASA's Jet
Propulsion Laboratory.
permanent storage
n. A recording medium that retains the data recorded on it for long periods of
time without power. Ink on paper is by far the most widely used permanent storage, but
data can be transferred from paper to a computer only with difficulty. Typically, some
form of magnetic medium, such as floppy disk or tape, is preferable. Magnetic media are
generally accepted as permanent, even though the magnetic fields that encode data in the
media tend to fade eventually (in five years or more). See also nonvolatile memory.
permanent swap file
n. In Windows, a file composed of contiguous disk sectors used for virtual
memory operations. See also swap file, virtual memory.
permission
n. In a networked or multiuser computer environment, the ability of a particular
user to access a particular resource by means of his or her user account. Permissions are
granted by the system administrator or other authorized person; these permissions are
stored in the system (often in a file called a permissions log) and are checked
when a user attempts to access a resource.
persistent link
n. See hot link (definition 1).
personal certificate
n. In Microsoft Internet Explorer, a personal certificate guarantees that you
are who you say you are. You specify information about yourself, such as your user name
and password. This information is used when you send personal information over the
Internet to a Web site that requires a certificate verifying your identity.See also
certificate, digital ID, web site certificate.
personal computer
n. A computer designed for use by one person at a time. Personal computers do
not need to share the processing, disk, and printer resources of another computer. IBM
PC-compatible computers and Apple Macintoshes are both examples of personal computers. Acronym:
PC.
peta-
prefix. Abbreviated P. Denotes 1 quadrillion (1015). In computing,
which is based on the binary (base-2) numbering system, peta- has a literal value
of 1,125,899,906,842,624, which is the power of 2 (250) closest to 1
quadrillion.
petabyte
n. Abbreviated PB. Either 1 quadrillion bytes or 1,125,899,906,842,624 bytes.
PGP
n. Acronym for Pretty Good Privacy. A program for public key encryption, using
the RSA algorithm, developed by Philip Zimmermann. PGP software is available in
unsupported free versions and supported commercial versions from Pretty Good Privacy,
Inc., Redwood Shores, Calif. See also privacy, public key encryption, RSA
encryption.
phase modulation
n. A method of imposing information onto a waveform signal by shifting the phase
of the wave to represent information, such as the binary digits 0 and 1. See also
phase-shift keying.
Phoenix BIOS
n. An IBM-compatible ROM BIOS manufactured by Phoenix Technologies, Ltd. A
popular ROM BIOS in many so-called PC "clone" computers, the Phoenix BIOS was an
early leader in IBM-compatible computers shortly after they began to appear in the
marketplace. See also BIOS, ROM BIOS. Compare AMI BIOS.
phone connector
n. An attachment, usually an RJ-11 connector, used to join a telephone line to a
device such as a modem.
PhotoCD
n. A digitizing system from Kodak that allows 35mm film pictures, negatives,
slides, and scanned images to be stored on a compact disc. Images are stored in a file
format called Kodak PhotoCD IMAGE PAC File Format, or PCD. Many photography or film
development businesses offer this service. Images stored on a PhotoCD can usually be
viewed by any computer with CD-ROM capabilities and the software required to read PCD.
Such images can also be viewed using one of a variety of players designed to display
images stored on CDs.
photo editor
n. A graphics application used to manipulate an image, such as a scanned
photograph, digitally.
photorealism
n. The process of creating images that are as close to photographic or
"real-life" quality as possible. In computer graphics, photorealism requires
powerful computers and highly sophisticated software and is heavily mathematical. See
also ray tracing.
phototypesetter
n. A printer similar to a laser printer but capable of resolutions over 2000
dots per inch. Phototypesetters apply light directly to a photographic film or
photosensitive paper. See also photocomposition. Compare imagesetter.
physical
adj. In computing, of, pertaining to, or characteristic of a real, as opposed to
a conceptual, piece of equipment or frame of reference. Compare logical (definition
2).
physical address
n. An address that corresponds to a hardware memory location. In simple
processors such as the 8088 and the 68000, every address is a physical address. In
processors supporting virtual memory, programs reference virtual addresses, which are then
mapped by memory management hardware onto physical addresses. See also memory
management unit, paging, virtual memory.
physical layer
n. The first, or lowest, of the seven layers in the International Organization
for Standardization's Open Systems Interconnection (OSI) model for standardizing
computer-to-computer communications. The physical layer is totally hardware-oriented and
deals with all aspects of establishing and maintaining a physical link between
communicating computers. Among specifications covered on the physical layer are cabling,
electrical signals, and mechanical connections. See also ISO/OSI model.
physical memory
n. Memory actually present in the system, as opposed to virtual memory. A
computer might have only 4 megabytes of physical RAM but support a virtual memory capacity
of 20 MB. Compare virtual memory.
PIC
n. See programmable interrupt controller.
pica
n. 1. With reference to typewriters, a fixed-width type font that fits 10
characters to the linear inch. See also pitch (definition 1). 2. As used by
typographers, a unit of measure equal to 12 points or approximately 1/6 inch. See also
point1 (definition 1).
pico-
prefix. Abbreviated p. Denotes one trillionth (10-12), or, in the
British numbering system, one million millionth.
picoJava
n. A microprocessor developed by Sun Microsystems, Inc., that executes Java
code. See also Java.
picosecond
n. Abbreviated psec. One trillionth of a second.
PICS
n. Acronym for Platform for Internet Content Selection. A standard for enabling
users to filter their Web access automatically using software (such as Internet Explorer
3.0) that detects codes for ratings in the sites' HTML files. In addition to filtering out
undesirable material, PICS can be used to screen sites according to whether they contain
material of interest. Several rating systems, emphasizing different sets of criteria, are
in use.
PICT
n. A file-format standard for encoding graphical images, both object-oriented
and bitmapped. The PICT file format was first used in Apple Macintosh applications, but
many IBM PC-compatible applications can read the format too. See also bitmapped
graphics, object-oriented graphics.
PID
n. Short for product identification number.
pie chart
n. A type of graph that presents values as percentages (slices) of a whole (a
pie).
PIM
n. Acronym for personal information manager. An application that usually
includes an address book and organizes unrelated information, such as notes, appointments,
and names, in a useful way.
pin
n. A slender prong. Pins are commonly encountered as the contacts protruding
from a male connector. Connectors are often identified by the number of pins they have.
Other types of pins are the spidery, leglike metal appendages that connect computer chips
to sockets on a circuit board or directly to the circuit board.
PIN
n. Acronym for personal identification number. A unique code number assigned, as
with automatic teller machine cards, to the authorized user.
ping1
n. 1. Acronym for Packet Internet Groper. A protocol for testing whether a
particular computer is connected to the Internet by sending a packet to its IP address and
waiting for a response. The name actually comes from submarine active sonar, where a sound
signal--called a "ping"--is broadcast, and surrounding objects are revealed by
their reflections of the sound. 2. A UNIX utility that implements the ping protocol.
ping2
vb. 1. To test whether a computer is connected to the Internet using the ping
utility. 2. To test which users on a mailing list are current by sending e-mail to the
list asking for a response.
Ping of Death
n. A form of Internet vandalism that entails sending a packet that is
substantially larger than the usual 64 bytes over the Internet via the ping protocol to a
remote computer. The size of the packet causes the computer to crash or reboot. See
also packet (definition 2), ping1 (definition 1).
pinout
n. A description or diagram of the pins of a chip or connector. See also
pin.
pipe
n. 1. A portion of memory that can be used by one process to pass information
along to another. Essentially, a pipe works like its namesake: it connects two processes
so that the output of one can be used as the input to the other. See also input
stream, output stream. 2. The vertical line character (|) that appears on a PC keyboard as
the shift character on the backslash (\) key. 3. In UNIX, a command function that
transfers the output of one command to the input of a second command.
pipeline processing
n. A method of processing on a computer that allows fast parallel processing of
data. This is accomplished by overlapping operations using a pipe, or a portion of
memory that passes information from one process to another. See also parallel
processing, pipe (definition 1), pipelining (definition 3).
piracy
n. 1. The theft of a computer design or program. 2. Unauthorized distribution
and use of a computer program.
pixel
n. Short for picture (pix) element. One spot in a rectilinear grid of thousands
of such spots that are individually "painted" to form an image produced on the
screen by a computer or on paper by a printer. A pixel is the smallest element that
display or print hardware and software can manipulate in creating letters, numbers, or
graphics. Also called pel.
pixel image
n. The representation of a color graphic in a computer's memory. A pixel image
is similar to a bit image, which also describes a screen graphic, but a pixel image has an
added dimension, sometimes called depth, that describes the number of bits in memory
assigned to each on-screen pixel.
pixel map
n. A data structure that describes the pixel image of a graphic, including such
features as color, image, resolution, dimensions, storage format, and number of bits used
to describe each pixel. See also pixel, pixel image.
PKUNZIP
n. A shareware utility program that uncompresses files compressed by the PKZIP
shareware utility program. PKUNZIP is generally made available with PKZIP; distribution of
PKUNZIP for commercial purposes is not permitted without permission from its publisher,
PKware, Inc. See also PKZIP.
PKZIP
n. A widely used shareware utility program for compressing files. Developed by
PKware, Inc., in 1989 and available from a wide variety of sources, PKZIP can combine one
or more files into a compressed output file having the extension .zip. A companion utility
program, PKUNZIP, is required to uncompress the compressed files. See also PKUNZIP,
shareware, utility program.
PLA
n. Acronym for programmable logic array. See field-programmable logic
array.
plaintext
n. 1. Nonencrypted or decrypted text. See also decryption, encryption. 2.
A file that is stored as plain ASCII data.
plain vanilla
adj. Ordinary; the standard version of hardware or software without any
enhancements. For example, a plain vanilla modem might have data transfer capability but
no fax or voice features.
platform
n. 1. The foundation technology of a computer system. Because computers are
layered devices composed of a chip-level hardware layer, a firmware and operating-system
layer, and an applications program layer, the bottommost layer of a machine is often
called a platform. 2. In everyday usage, the type of computer or operating system being
used.
platter
n. One of the individual metal data storage disks within a hard disk drive. Most
hard disks have from two to eight platters. See also hard disk.
PL/C
n. A version of the PL/I programming language developed at Cornell University
and used on mainframe computers. See also PL/I.
plot
vb. To create a graphic or a diagram by connecting points representing variables
(values) that are defined by their positions in relation to a horizontal (x) axis
and a vertical (y) axis (and sometimes a depth, or z, axis).
plotter
n. Any device used to draw charts, diagrams, and other line-based graphics.
Plotters use either pens or electrostatic charges and toner. Pen plotters draw on paper or
transparencies with one or more colored pens. Electrostatic plotters "draw" a
pattern on electrostatically charged dots on the paper and then apply toner and fuse it in
place. Plotters use three basic types of paper handling: flatbed, drum, and pinch roller.
Flatbed plotters hold the paper still and move the pen along both x and y
axes. Drum plotters roll the paper over a cylinder. The pen moves along one axis while the
drum, with the paper attached, moves along the other. Pinch-roller plotters are a hybrid
of the two, in which the pen moves only along one axis while the paper is moved back and
forth by small rollers.
Plug and Play
n. A set of specifications developed by Intel that allows a PC to configure
itself automatically to work with peripherals such as monitors, modems, and printers. A
user can "plug" in a peripheral and "play" it without manually
configuring the system. A Plug and Play PC requires both a BIOS that supports Plug and
Play and a Plug and Play expansion card. See also BIOS, expansion board,
peripheral.
plug-in
n. 1. A small software program that plugs into a larger application to provide
added functionality. 2. A software component that plugs into the Netscape Navigator.
Plug-ins permit the Web browser to access and execute files embedded in HTML documents
that are in formats the browser normally would not recognize, such as many animation,
video, and audio files. Most plug-ins are developed by software companies who have
proprietary software in which the embedded files are created. Compare helper
application, helper program.
PNG
n. Short for Portable Network Graphics.
PNP transistor
n. A type of bipolar transistor in which a base of N-type material is sandwiched
between an emitter and a collector of P-type material. The base, emitter, and collector
are the three terminals of the transistor through which current flows. In a PNP
transistor, holes (electron "vacancies") are the majority of the charge
carriers, and they flow from the emitter to the collector. See also N-type
semiconductor, P-type semiconductor. Compare NPN transistor.
point1
n. 1. A unit of measure used in printing, equal to approximately 1/72
of an inch. Character height and the amount of space (leading) between lines of text are
usually specified in points. 2. A single pixel on the screen, identified by its row and
column numbers. 3. A location in a geometric form, represented by two or more numbers that
constitute its coordinates.
point2
vb. To move an arrow or other such indicator to a particular item or position on
the screen by using direction keys or by maneuvering a pointing device such as a mouse.
point-and-click
adj. Enabling a user to select data and activate programs by using a mouse or
other pointing device to move a cursor to a desired location ("point") and
pressing a button on the mouse or other pointing device ("click").
PointCast
n. An Internet service that delivers and displays a personalized set of news
articles to individual users. Unlike the World Wide Web and other Internet applications,
PointCast is a push technology, where the server automatically uploads data without
a specific command from the client. See also server (definition 2).
pointing device
n. An input device used to control an on-screen cursor for such actions as
"pressing" on-screen buttons in dialog boxes, choosing menu items, and selecting
ranges of cells in spreadsheets or groups of words in a document. A pointing device is
often used to create drawings or graphical shapes. The most common pointing device is the
mouse, which was popularized by its use with the Apple Macintosh. Other pointing devices
include graphics tablets, styluses, light pens, joysticks, pucks, and trackballs. See
also graphics tablet, joystick, light pen, mouse, puck, stylus, trackball.
point of presence
n. 1. A point in a wide area network to which a user can connect with a local
telephone call. 2. A point at which a long distance telephone carrier connects to a local
telephone exchange or to an individual user. Acronym: POP.
Point-to-Point Tunneling Protocol
n. A specification for virtual private networks in which some nodes of a local
area network are connected through the Internet. See also virtual network. Acronym:
PPTP.
polymorphism
n. In an object-oriented programming language, the ability to redefine a routine
in a derived class (a class that inherited its data structures and routines from another
class). Polymorphism allows the programmer to define a base class that includes routines
that perform standard operations on groups of related objects, without regard to the exact
type of each object. The programmer then redefines the routines in the derived class for
each type, taking into account the characteristics of the object. See also class,
derived class, object (definition 2), object-oriented programming.
Pong
n. The first commercial video game, a table tennis simulation, created by Nolan
Bushnell of Atari in 1972.
POP3
n. Acronym for Post Office Protocol 3. This is the current version of the Post
Office Protocol standard in common use on TCP/IP networks. See also Post Office
Protocol, TCP/IP.
populate
vb. 1. To put chips in the sockets of a circuit board. 2. To import prepared
data into a database from a file using a software procedure rather than by having a human
operator enter individual records.
pop-up Help
n. An online help system whose messages appear as pop-up windows when the user
clicks on a topic or area of the screen about which help is desired. Typically, a special
form of click, such as clicking the right mouse button or Option-clicking, will activate
pop-up Help, if it is available. See also balloon help.
pop-up menu
or popup menu n. In a graphical user interface, a menu that appears on-screen
when a user selects a certain item. Pop-up menus can appear anywhere on the screen and
generally disappear when the user selects an item in the menu. Also called popup. Compare
drop-down menu, pull-down menu.
pop-up messages
n. The messages that appear when pop-up Help is used.
pop-up window
n. A window that appears when an option is selected. Typically, the window
remains visible until the mouse button is released.
port1
n. One of the network input/output channels of a computer running TCP/IP. On the
World Wide Web, port usually refers to the port number a server is running on. A single
computer can have many Web servers running on it, but only one server can be running on
each port. The default port for Web servers is 80. See input/output port.
port2
vb. 1. To change a program in order to be able to run it on a different
computer. 2. To move documents, graphics, and other files from one computer to another.
portable
adj. 1. Capable of running on more than one computer system or under more than
one operating system. Highly portable software can be moved to other systems with little
effort, moderately portable software can be moved only with substantial effort, and
nonportable software can be moved only with effort similar to or greater than the effort
of writing the original program. 2. Light enough, rugged enough, and free enough of
encumbering external connections to be carried by a user.
portable computer
n. Any computer designed to be moved easily. Portable computers can be
characterized by size and weight as in the table below. k:\compdict\database\5011.doc
Portable Distributed Objects
n. Software from NeXT, running under UNIX, that supports an object model in
which objects to be stored at various locations on a network can be accessed as though
they were at a single location. Acronym: PDO.
Portable Document Format
n. The Adobe specification for electronic documents that use the Adobe Acrobat
family of servers and readers. See also Acrobat, .pdf. Acronym: PDF.
Portable Network Graphics
n.New bitmapped graphics format conforming to the Portable Network Graphics
Tenth Specification (Version 1.0). PNG format is similar to GIF (Graphics Interchange
Format), however, it does not use patented data compression and is license-free. The World
Wide Web consortium approved it as a standard to replace GIF. PNG is supported in the
latest versions of Microsoft Internet Explorer and Netscape Navigator.
portrait mode
n. A vertical print orientation in which a document is printed across the
narrower dimension of a rectangular sheet of paper. This is the print mode typical of most
letters, reports, and other such documents. Compare landscape mode.
POS
n. Acronym for point of sale. The place in a store at which goods are paid for.
Computerized transaction systems, such as those in use at automated supermarkets, use
scanners for reading tags and bar codes, electronic cash registers, and other special
devices to record purchases at this point.
POSIX
n. Acronym for Portable Operating System Interface for UNIX. An IEEE standard
that defines a set of operating-system services. Programs that adhere to the POSIX
standard can be easily ported from one system to another. POSIX was based on UNIX system
services, but it was created in a way that allows it to be implemented by other operating
systems.
post
vb. To submit an article in a newsgroup or other online conference. The term is
derived from the "posting" of a notice on a physical bulletin board. See also
newsgroup.
postmaster
n. The logon name (and therefore the e-mail address) of an account that is
responsible for maintaining e-mail services on a mail server. When an accountholder is
having trouble with e-mail, a message to "postmaster" or
"postmaster@machine.org.domain.name" will usually reach a human who can solve
the problem.
Post Office Protocol
n. A protocol for servers on the Internet that receive, store, and transmit
e-mail and for clients on computers that connect to the servers to download and upload
e-mail. Acronym: POP.
PostScript
n. A page-description language from Adobe Systems that offers flexible font
capability and high-quality graphics. The most well-known page-description language,
PostScript uses English-like commands to control page layout and to load and scale outline
fonts. Adobe Systems is also responsible for Display PostScript, a graphics language for
computer displays that gives users of both PostScript and Display PostScript absolute
WYSIWYG (what-you-see-is-what-you-get), which is difficult when different methods are used
for displaying and printing. See also outline font, page-description language.
PostScript font
n. A font defined in terms of the PostScript page-description language rules and
intended to be printed on a PostScript-compatible printer. PostScript fonts are
distinguished from bitmapped fonts by their smoothness, detail, and faithfulness to
standards of quality established in the typographic industry. See also PostScript. Compare
screen font.
POTS
n. Acronym for Plain Old Telephone Service. Basic dial telephone connections to
the public switched network, without any added features or functions. A POTS line is
nothing but a phone line connected to a simple desktop telephone instrument.
PowerBook
n. Any of several computers in the family of portable Macintosh computers made
by Apple.
power down
vb. To shut down (a computer); to turn off the power.
power failure
n. Loss of electricity, which causes a loss of unsaved data in a computer's
random access memory (RAM) if no backup power supply is connected to the machine. Compare
surge.
Power Macintosh
n. An Apple Macintosh computer based on the PowerPC processor. The first Power
Macintoshes, 6100/60, 7100/66, and 8100/80, were unveiled in March 1994. Also called
Power Mac. See also PowerPC.
Power-on key
n. A special key on the Apple ADB and Extended keyboards used for turning on a
Macintosh II. The Power-on key is marked with a left-pointing triangle and is used in lieu
of the on/off switch. There is no Power-off key; the system is shut down by choosing the
Shut Down command from the Special menu.
power-on self test
n. A set of routines stored in a computer's read-only memory (ROM) that tests
various system components such as RAM, the disk drives, and the keyboard to see if they
are properly connected and operating. If problems are found, these routines alert the user
by sounding a series of beeps or displaying a message, often accompanied by a diagnostic
numeric value, to the standard output or standard error device (usually the screen). If
the power-on self test is successful, it passes control to the system's bootstrap loader. See
also bootstrap loader. Acronym: POST.
PowerPC
n. A microprocessor architecture developed in 1992 by Motorola and IBM, with
some participation by Apple. A PowerPC microprocessor is RISC-based and superscalar, with
a 64-bit data bus and a 32-bit address bus. It also has separate data and instruction
caches, although the size of each varies by implementation. All PowerPC microprocessors
have multiple integer and floating-point units, and all have an operating voltage of 3.3
volts, except for the 601, which operates at 3.6 volts. The operating speed and number of
instructions executed per clock cycle varies with the implementation. The 601 is available
in a 80-MHz or 100-MHz version and executes three instructions per clock cycle. The 603,
available in 80-MHz, 100-MHz, and 200-MHz versions, executes three instructions per clock
cycle. The 604, available in 100-MHz, 120-MHz, and 133-MHz versions, executes four
instructions per clock cycle. The 620, available in a 133-MHz version, also executes four
instructions per clock cycle. PowerPC is a registered trademark of IBM. See also
microprocessor, RISC.
PowerPC Platform
n. A platform developed by IBM, Apple, and Motorola based on the 601 and later
chips. This platform supports the use of multiple operating systems such as Mac OS,
Windows NT, and AIX as well as software designed for those individual operating systems.
PowerPC Reference Platform
n. An open system standard developed by IBM. IBM's goal in designing the PowerPC
Reference Platform was to ensure compatibility among PowerPC systems built by different
companies. Apple's PowerPC Macintoshes are not yet compliant with the PowerPC Reference
Platform, but future versions are expected to be. See also Common Hardware
Reference Platform, open system, PowerPC. Acronym: PPCP., PReP (prep, P`R-E-P').
power supply
n. An electrical device that transforms standard wall outlet electricity (115-120
VAC in the United States) into the lower voltages (typically 5 to 12 volts DC) required by
computer systems. Personal computer power supplies are rated by wattage; they usually
range from about 90 watts at the low end to 250 watts at the high end.
power up
vb. To start up a computer; to begin a cold boot procedure; to turn on the
power.
power user
n. A person adept with computers, particularly on an applications-oriented level
rather than on a programming level. A power user is someone who knows a considerable
amount about computers and is comfortable enough with applications to be able to work with
their most sophisticated features.
PPP
n. Acronym for Point-to-Point Protocol. A data link protocol developed by the
Internet Engineering Task Force in 1991 for dial-up telephone connections, such as between
a computer and the Internet. PPP provides greater protection for data integrity and
security than does SLIP, at a cost of greater overhead. Compare SLIP.
PPTP
See Point-to-Point Tunneling Protocol.
PRAM
n. Short for parameter RAM. A portion of RAM in Macintosh computers that
contains configuration information such as the date and time, desktop pattern, and other
control panel settings. See also RAM.
P-rating
n. Short for performance rating. A microprocessor rating system by IBM, Cyrix,
and others, based on throughput in realistic applications. Formerly, microprocessor clock
speed was widely used as a method of rating, but it does not account for differing chip
architectures or different types of work people do with computers. See also central
processing unit, clock (definition 1), microprocessor.
preemptive multitasking
n. A form of multitasking in which the operating system periodically interrupts
the execution of a program and passes control of the system to another waiting program.
Preemptive multitasking prevents any one program from monopolizing the system. Also
called time-slice multitasking. See also multitasking.
Preferences
n. A menu choice in many graphical user interface applications that allows the
user to specify how the application will act each time it is used. For example, in a word
processing application the user may be allowed to specify whether the ruler will appear,
whether the document will appear in the same way as it will print (including margins), and
other choices. Also called Options, Prefs.
presentation graphics
n. The representation of business information, such as sales figures and stock
prices, in chart form rather than as lists of numbers. Presentation graphics are used to
give viewers an immediate grasp of business statistics and their significance. Common
examples are area charts, bar charts, line charts, and pie charts. Also called
business graphics.
presentation layer
n. The sixth of the seven layers in the International Organization for
Standardization's Open Systems Interconnection (ISO/OSI) model for standardizing
computer-to-computer communications. The presentation layer is responsible for formatting
information so that it can be displayed or printed. This task generally includes
interpreting codes (such as tabs) related to presentation, but it can also include
converting encryption and other codes and translating different character sets. See
also ISO/OSI model.
Presentation Manager
n. The graphical user interface provided with OS/2 versions 1.1 and later. The
Presentation Manager derives from the MS-DOS-based Windows environment and provides
similar capabilities. The user sees a graphical, window-oriented interface, and the
programmer uses a standard set of routines for handling screen, keyboard, mouse, and
printer input and output, no matter what hardware is attached to the system. See also
OS/2, Windows.
preventive maintenance
n. Routine servicing of hardware intended to keep equipment in good operating
condition and to find and correct problems before they develop into severe malfunctions.
preview
n. In word processors and other applications, the feature that displays a
formatted document on the video monitor rather than sending it directly to the printer.
primary channel
n. The data-transmission channel in a communications device, such as a modem. Compare
secondary channel.
Primary Domain Controller
n. 1. In Windows NT, a database providing a centralized administration site for
resources and user accounts. The database allows users to log onto the domain, rather than
onto a specific host machine. A separate account database keeps track of the machines in
the domain and allocates the domain's resources to users. 2. In any local area network,
the server that maintains the master copy of the domain's user accounts database and that
validates logon requests. Acronym: PDC.
primitive
n. 1. In computer graphics, a shape, such as a line, circle, curve, or polygon,
that can be drawn, stored, and manipulated as a discrete entity by a graphics program. A
primitive is one of the elements from which a large graphic design is created. 2. In
programming, a fundamental element in a language that can be used to create larger
procedures that do the work a programmer wants to do.
printer
n. A computer peripheral that puts text or a computer-generated image on paper
or on another medium, such as a transparency film. Printers can be categorized in any of
several ways. The most common distinction is impact versus nonimpact. Impact printers
physically strike the paper and are exemplified by pin dot-matrix printers and daisy-wheel
printers; nonimpact printers include every other type of print mechanism, including laser,
ink-jet, and thermal printers. Other possible methods of categorizing printers include
(but are not limited to) the following: See also ball printer, character printer,
color printer, daisy-wheel printer, dot-matrix printer, draft quality, electrophotographic
printers, graphics printer, impact printer, ink-jet printer, ion-deposition printer, laser
printer, LCD printer, LED printer, letter quality, line printer, near-letter-quality,
nonimpact printer, page printer, parallel printer, serial printer, thermal printer,
thermal wax-transfer printer, thimble printer. k:\compdict\database\4548.doc
Printer Control Language
n. A printer control language from Hewlett-Packard, used in its LaserJet,
DeskJet, and RuggedWriter printer lines. Because of the LaserJet's dominance in the laser
printer market, Printer Control Language has become a de facto standard. Also called
Hewlett-Packard Printer Control Language, PCL. Acronym: PCL.
printer controller
n. The processing hardware in a printer, especially in a page printer. It
includes the raster image processor, the memory, and any general-purpose microprocessors.
A printer controller can also reside in a personal computer, attached via a high-speed
cable to a printer that simply carries out its instructions. Compare printer
engine.
printer driver
n. A software program designed to enable other programs to work with a
particular printer without concerning themselves with the specifics of the printer's
hardware and internal "language." Application programs can communicate properly
with a variety of printers by using printer drivers, which handle all of the subtleties of
each printer so that the application program doesn't have to. Today graphical user
interfaces offer their own printer drivers, eliminating the need for an application that
runs under the interface to have its own printer driver.
printer font
n. A font residing in or intended for a printer. A printer font can be internal,
downloaded, or on a font cartridge. Compare screen font.
printer port
n. A port through which a printer can be connected to a personal computer. On
PC-compatible machines, printer ports are usually parallel ports and are identified in the
operating system by the logical device name LPT. On many newer PCs, the parallel port on
the case of the CPU has a printer icon beside it to identify it as a printer port. Serial
ports can also be used for some printers (logical device name COM), although configuration
is generally required. On Macintoshes, printer ports are usually serial ports and are also
used to connect Macs to an AppleTalk network. See also AppleTalk, central
processing unit, logical device, parallel port, serial port.
print job
n. A single batch of characters printed as a unit. A print job usually consists
of a single document, which can be one page or hundreds of pages long. To avoid having to
print individual documents separately, some software can group multiple documents into a
single print job. See also print spooler.
print quality
n. The quality and clarity of characters produced by a printer. Print quality
varies with the type of printer; in general, dot-matrix printers produce lower-quality
output than laser printers. The printer mode can also affect quality. See also
resolution (definition 1).
print queue
n. A buffer for documents and images waiting to be printed. When an application
places a document in a print queue, it is held in a special part of the computer's memory,
where it waits until the printer is ready to receive it.
Print Screen key
n. A key on IBM PC and compatible keyboards that normally causes the computer to
send a character-based "picture" of the screen contents to the printer. The
print screen feature works only when the display is in text mode or CGA graphics mode (the
lowest-resolution color and graphics mode available on IBM compatibles). It will not work
properly in other graphics modes. Some programs use the Print Screen key to capture a
screen image and record it as a file on disk. These programs can typically work in any
graphics mode and record the file as a graphics image. When the user is working directly
with the MS-DOS operating system, and with some programs, the combination Control-Print
Screen toggles the printer on or off. With printing turned on, the system sends every
character to the printer as well as to the screen. The Print Screen key on the Apple
Extended Keyboard is included for compatibility with operating systems such as MS-DOS. Also
called PrtSc key.
print server
n. A workstation that is dedicated to managing printers on a network. The print
server can be any station on the network.
print spooler
n. Computer software that intercepts a print job on its way to the printer and
sends it to disk or memory instead, where the print job is held until the printer is ready
for it. The term spooler is an acronym created from "simultaneous peripheral
operations on line."
print to file
n. A command in many applications that instructs the program to format a
document for printing and store the formatted document as a file rather than sending it to
a printer.
privacy
n. The concept that a user's data, such as stored files and e-mail, is not to be
examined by anyone else without that user's permission. A right to privacy is not
generally recognized on the Internet. Federal law protects only e-mail in transit or in
temporary storage, and only against access by Federal agencies. Employers often claim a
right to inspect any data on their systems. To obtain privacy, the user must take active
measures such as encryption. See also encryption, PGP, Privacy Enhanced Mail. Compare
security.
Privacy Enhanced Mail
n. An Internet standard for e-mail systems that use encryption techniques to
ensure the privacy and security of messages. See also encryption, standard. Compare
PGP. Acronym: PEM.
Private Communications Technology
n. A specification designed to secure general-purpose business and personal
communications on the Internet, and includes features such as privacy, authentication, and
mutual identification.
private folders
n. In a shared network environment, those folders on a user's computer that are
not currently accessible by other users on the network. Compare public folders.
private key
n. One of two keys in public key encryption. The user keeps the private key
secret and uses it to encrypt digital signatures and to decrypt received messages. See
also public key encryption. Compare public key.
procedure call
n. In programming, an instruction that causes a procedure to be executed. A
procedure call can be located in another procedure or in the main body of the program. See
also procedure.
process1
n. A program or part of a program; a coherent sequence of steps undertaken by a
program.
process2
vb. To manipulate data with a program.
process color
n. A method of handling color in a document in which each block of color is
separated into its subtractive primary color components for printing: cyan, magenta, and
yellow (as well as black). All other colors are created by blending layers of various
sizes of halftone spots printed in cyan, magenta, and yellow to create the image. See
also color model, color separation (definition 1). Compare spot color.
processing
n. The manipulation of data within a computer system. Processing is the vital
step between receiving data (input) and producing results (output)--the task for which
computers are designed.
processor
n. See central processing unit, microprocessor.
progressive JPEG
n. An enhancement to the JPEG image format specification that allows an image to
be gradually displayed in a Web browser, showing increasingly detailed versions of the
entire image until all of the data has finished downloading. While this is similar to
interlaced GIF images, progressive JPEG images can retain the high quality of 24-bit color
and offer the same efficient compression as standard JPEG. See also JPEG. Compare
interlaced GIF.
Prodigy Information Service
n. An online information service founded by IBM and Sears. Like its competitors
America Online and CompuServe, Prodigy offers access to databases and file libraries,
online chat, special interest groups, e-mail, and Internet connectivity. Also called
Prodigy.
Product Identification Number
n.An identification number that appears either on the bottom of a device or on
the opening screen or in the About dialog box of an application program.
profile
vb. To analyze a program to determine how much time is spent in different parts
of the program during execution.
program
n. A sequence of instructions that can be executed by a computer. The term can
refer to the original source code or to the executable (machine language) version. Also
called software. See also program creation, routine, statement.
program file
n. A disk file that contains the executable portion(s) of a computer program.
Depending on its size and complexity, an application or other program, such as an
operating system, can be stored in several different files, each containing the
instructions necessary for some part of the program's overall functioning. Compare
document file.
programmable
adj. Capable of accepting instructions for performing a task or an operation.
Being programmable is a characteristic of computers.
programmer
n. 1. An individual who writes and debugs computer programs. Depending on the
size of the project and the work environment, a programmer might work alone or as part of
a team, be involved in part or all of the process from design through completion, or write
all or a portion of the program. See also program. 2. In hardware, a device used to
program read-only memory chips. See also PROM, ROM (definition 2).
programming
n. The art and science of creating computer programs. Programming begins with
knowledge of one or more programming languages, such as Basic, C, Pascal, or assembly
language. Knowledge of a language alone does not make a good program. Much more can be
involved, such as expertise in the theory of algorithms, user interface design, and
characteristics of hardware devices. Computers are rigorously logical machines, and
programming requires a similarly logical approach to designing, writing (coding), testing,
and debugging a program. Low-level languages, such as assembly language, also require
familiarity with the capabilities of a microprocessor and the basic instructions built
into it. In the modular approach advocated by many programmers, a project is broken into
smaller, more manageable modules--stand-alone functional units that can be designed,
written, tested, and debugged separately before being incorporated into the larger
program. See also algorithm, kludge (definition 2), modular design, object-oriented
programming, spaghetti code, structured programming.
programming language
n. Any artificial language that can be used to define a sequence of instructions
that can ultimately be processed and executed by the computer. Defining what is or is not
a programming language can be tricky, but general usage implies that the translation
process--from the source code expressed using the programming language to the machine code
that the computer needs to work with--be automated by means of another program, such as a
compiler. Thus, English and other natural languages are ruled out, although some subsets
of English are used and understood by some fourth-generation languages. See also
4GL, compiler (definition 2), natural language, program.
project life cycle
n. A sequence of preplanned stages for taking a project from beginning to end.
project management
n. The process of planning, monitoring, and controlling the course and
development of a particular undertaking.
PROM
n. Acronym for programmable read-only memory. A type of read-only memory (ROM)
that allows data to be written into the device with hardware called a PROM programmer.
After a PROM has been programmed, it is dedicated to that data, and it cannot be
reprogrammed. See also EEPROM, EPROM, ROM (definition 2).
promiscuous-mode transfer
n. In network communications, a transfer of data in which a node accepts all
packets regardless of their destination address.
prompt
n. 1. In command-driven systems, one or more symbols that indicate where users
are to enter commands. For instance, in MS-DOS, the prompt is generally a drive letter
followed by a "greater than" symbol (C>). In Unix, it is usually %. See
also command-driven system, DOS prompt. 2. Displayed text indicating that a computer
program is waiting for input from the user.
property
n. In Windows 95, a characteristic or parameter of an object or device.
Properties of a file, for example, include type, size, and creation date and can be
identified by accessing the file's property sheet. See also property sheet.
property sheet
n. A type of dialog box in Windows 95, accessed by choosing Properties in the
File menu or by right-clicking on an object and selecting Properties, that lists the
attributes or settings of an object such as a file, application, or hardware device. A
property sheet presents the user with a tabbed, index-card-like selection of property
pages, each of which features standard dialog-style controls for customizing parameters.
proportional font
n. A set of characters in a particular style and size in which a variable amount
of horizontal space is allotted to each letter or number. In a proportional font, the
letter i, for example, is allowed less space than the letter m. Compare
monospace font.
proportional spacing
n. A form of character spacing in which the horizontal space each character
occupies is proportional to the width of the character. The letter w, for example,
takes up more space than the letter i. Compare monospacing.
proprietary
adj. Of, pertaining to, or characteristic of something that is privately owned.
Generally, the term refers to technology that has been developed by a particular
corporation or entity, with specifications that are considered by the owner to be trade
secrets. Proprietary technology may be legally used only by a person or entity purchasing
an explicit license. Also, other companies are unable to duplicate the technology, both
legally and because its specifications have not been divulged by the owner. Compare
public domain.
proprietary software
n. A program owned or copyrighted by an individual or a business and available
for use only through purchase or by permission of the owner. Compare public-domain
software.
protected mode
n. An operating mode of the Intel 80286 and higher microprocessors that supports
larger address spaces and more advanced features than real mode. When started in protected
mode, these CPUs provide hardware support for multitasking, data security, and virtual
memory. The Windows NT and OS/2 operating systems run in protected mode, as do most
versions of UNIX for these microprocessors. Compare real mode.
protocol stack
n. The set of protocols that work together on different levels to enable
communication on a network. For example, TCP/IP, the protocol stack on the Internet,
incorporates more than 100 standards including FTP, IP, SMTP, TCP, and Telnet. Also
called protocol suite. See also ISO/OSI model.
prototyping
n. The creation of a working model of a new computer system or program for
testing and refinement. Prototyping is used in the development of both new hardware and
software systems and new systems of information management. Tools used in the former
include both hardware and support software; tools used in the latter can include
databases, screen mockups, and simulations that, in some cases, can be developed into a
final product.
proxy server
n. A firewall component that manages Internet traffic to and from a local area
network (LAN) and can provide other features, such as document caching and access control.
A proxy server can improve performance by supplying frequently requested data, such as a
popular Web page, and can filter and discard requests that the owner does not consider
appropriate, such as requests for unauthorized access to proprietary files. See also
firewall.
PSN
n. Acronym for packet-switching network. See packet switching.
public directory
n. A directory on an FTP server that is accessible by anonymous users for the
purpose of retrieving or storing files. Often the directory is called /pub. See also
anonymous FTP, FTP (definition 1), FTP server, /pub.
public key
n. One of two keys in public key encryption. The user releases this key to the
public, who can use it for encrypting messages to be sent to the user and for decrypting
the user's digital signature. See also public key encryption. Compare
private key.
public key encryption
n. An asymmetric scheme that uses a pair of keys for encryption: the public key
encrypts data, and a corresponding secret key decrypts it. For digital signatures, the
process is reversed: the sender uses the secret key to create a unique electronic number
that can be read by anyone possessing the corresponding public key, which verifies that
the message is truly from the sender. See also private key, public key.
pull
vb. The process of retrieving data from a network server. Compare push
(definition 2). See pop.
pull-down menu
n. A menu that is pulled down from the menu bar and that remains available as
long as the user holds it open. Compare drop-down menu.
punched card
n. An outdated computer-input medium made of stiff paper that stores data bits
in columns containing patterns of punched holes. The method for creating the patterns used
for different byte values is called Hollerith coding. Also called Hollerith
tabulating/recording machine.
punched-card reader
n. See card reader.
purge
vb. To eliminate old or unneeded information systematically; to clean up, as
files.
push
vb. 1. To add a new element to a stack, a data structure generally used to
temporarily hold pieces of data being transferred or the partial result of an arithmetic
operation. See also stack. Compare pop. 2. In networks and the Internet, to
send data or a program from a server to a client at the instigation of the server. Compare
pull (definition 1).
put
vb. In programming, to write data, typically to a file; in particular, to write
a very small unit of data, such as a character.
PVC
n. Acronym for permanent virtual circuit. A permanent logical connection between
two nodes on a packet-switching network. The PVC appears as a dedicated line to the nodes,
but the data can be transmitted on a common carrier. VPN. See also common carrier,
node (definition 2), packet switching. Compare SVC.
pwd
n. Acronym for print working directory. The UNIX command for displaying the
current directory.