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To convert data to a compact form in a storage medium by taking advantage of known characteristics of the data and of the storage medium, in such a way that the original form of the data can be recovered; for example, storing two decimal digits per octet instead of storing them as individual octets. Synonymous with compact. Contrast with compress.

In programming, a module designed to provide abstraction, encapsulation, or information hiding through grouping of logically related language constructs, such as data types, data objects of these data types, and subprograms with parameters of these data types.

package declaration:
The separate declaration of those language constructs whose specifications are required outside the package, either for interfacing (the visible part) or for compilation (the private part).

packed decimal notation:
A binary-coded decimal notation in which two consecutive decimal digits, each having four bits, are represented by one byte.

packed numeric:
A representation of numeric values that compresses each character representation in such a manner that the original value can be recovered.

In data communications, a sequence of bits arranged in a specific format, containing control data and possibly user data, and that is transmitted and switched as a whole.

packet assembler/disassembler (PAD):
A functional unit that enables data terminal equipment not equipped for packet transfer mode to access a packet switching network.

packet mode terminal:
Data terminal equipment that can control, format, transmit, and receive packets.

packet sequencing:
A process of ensuring that packets are delivered to the receiving data terminal equipment (DTE) in the same order as they were submitted by the sending DTE.

packet sniffer:
A functional unit that monitors the network traffic to recognize and decode packets of interest. A packet sniffer is used for network management.

packet switching:
In a data network, the process of routing and transferring data by means of addressed packets so that, between two nodes, each transmission channel is allocated dynamically to packets having different addresses. Contrast with circuit switching, message switching.

packet transfer mode:
A method of data transfer, by means of packet transmission and packet switching, that permits sharing of network resources among many connections.

The operation performed when data are packed.

packing density:
Deprecated synonym for data density.

packet assembler/disassembler.

The use of special techniques to protect data or software against unauthorized copying.

(1) In text processing, a physical or logical block of data that may be printed on a single sheet of paper or displayed on a screen. (2) In a virtual storage system, a fixed-length block of data that has a virtual address and is transferred as a unit.

page break:
A function that ends printing on the current page and restarts printing at the top of the next page.

page depth:
Synonym for page length.

page depth control:
Synonym for page length control.

page description language (PDL):
A text-formatting language used to specify the printed page or display image of a document, page by page; for example: HPGL, PostScript.

page footer:
A block of text printed at the bottom of one or more pages in a document. A page footer may contain varying information, such as a page number. Synonymous with running foot.

page frame:
In real memory, a segment of memory that has the size of a page.

page header:
A block of text printed at the top of one or more pages in a document. A page header may contain varying information, such as a page number.

page length:
The vertical dimension of the area available for printing or displaying on a screen or page. Synonymous with page depth.

page length control:
In text processing, the capability to specify the page length. Synonymous with page depth control.

page printer:
A printer that prints one page as a unit; for example, a COM printer, a laser printer.

page reader:
A character reader whose input data are printed text.

In text processing, the division of a document into pages, either by a user or automatically.

The transfer of pages between real memory and external storage.

paging device:
An external storage device used primarily to hold pages.

paging technique:
A technique by which real memory is divided into page frames.

PAL circuit:
Synonym for programmable array logic circuit.

panel interface:
A screen-oriented user interface designed to permit interactive processing.

In computer graphics, progressively translating the display elements to give the visual impression of lateral movement of the display image. During panning, display elements may be removed and others added to a display image. Synonymous with panoramic translating.

panoramic translating:
Synonym for panning.

Password Authentication Protocol

paper carrier:
An arrangement of components for holding and guiding the printing medium in a device.

paper feed:
A mechanism that moves paper through a printer or another device.

paper skip:
The movement of paper through a print mechanism at a speed effectively greater than that of individual single line spacing. Synonymous with paper slew, paper throw.

paper slew:
Synonym for paper skip.

paper throw:
Synonym for paper skip.

One or more sentences treated as a unit.

paragraph control:
In text processing, a capability to process text one paragraph at a time; for example: skip, move, delete, print.

paragraph indent:
In text processing, an instruction that indents one or more lines of a paragraph a preset number of characters or a preset distance.

(1) Pertaining to the simultaneous occurrence of events or processes for a common purpose. Processes may be similar or dissimilar; the emphasis is on the common purpose; for example: the transmission, in parallel, of the bits of a computer word. Contrast with serial. (2) Pertaining to a configuration of multiple devices designed to operate simultaneously, for a common purpose.

parallel computer:
A computer that has multiple arithmetic and logic units that are used to accomplish parallel operations or parallel processing. Contrast with serial computer.

parallel operation:
An operating mode in which operations are performed in parallel in one or more devices. Contrast with serial operation.

parallel port:
A port of a functional unit used to transfer multiple data units (e.g., bits or bytes) in parallel.

parallel processing:
The operating mode in which two or more processes are executed as concurrent or simultaneous processes.

parallel run:
Operation of two data processing systems, a given one and its intended replacement, with the same application and source data, for comparison and confidence.

parallel-search storage:
A storage device in which one or more parts of all storage locations may be queried or accessed simultaneously.

parallel-serial converter:
A functional unit for converting a group of signal elements, which are all presented simultaneously, into a corresponding sequence of consecutive signal elements, which represents the same information. Synonymous with serializer.

parallel transmission:
The simultaneous transmission over separate transmission channels of the signal elements of a group representing a character or other entity of data.

In programming languages, a language construct for passing data objects or data values between modules.

parameter association:
The association between formal parameters and their corresponding actual parameters in a call or generic instantiation.

parameter word:
A word that directly or indirectly provides or designates one or more parameters.

In computer vision, a blob that wholly surrounds another blob. Example: The red part of the flag of Switzerland is the parent of the white cross.

parent node:
A node to which at least one other node is directly subordinate.

parent type:
A data type that serves as the template for creating new data types. Contrast with base type, derived type.

To determine the syntactic structure of a language construct by decomposing it into lexical tokens and establishing the relationships among them; for example, to parse blocks into statements, statements into expressions, expressions into operators and operands.

A software tool that parses programs or other text, often as the first step of assembly, compilation, interpretation, or analysis.

partial correctness:
Correctness proving indicating that a program's output assertions follow logically from its input assertions and processing steps. Contrast with total correctness.

partial immersion:
An immersion when some actual reality is perceived.

partially connected network:
In artificial neural networks, a nonlayered network in which each artificial neuron is not necessarily connected to all the others, or a layered network in which each artificial neuron in a layer is not necessarily connected to all neurons in the adjacent forward layer. Synonymous with diluted network.

partially embossed optical disk:
An optical disk that contains both rewritable and embossed data in the data zone.

partially learned concept:
A concept whose precise description cannot be inferred on the basis of available data, knowledge, or assumptions.

A specific general-purpose, high-level procedure-oriented language with features that support and emphasize structured programming, data structures with strong typing, and modularity.

passive matrix display:
Synonym for passive matrix display device.

passive matrix display device:
A liquid-crystal display device that controls pixels, controlling their rows and columns. Synonymous with passive matrix display.

passive station:
On a multipoint connection or a point-to-point connection using basic mode link control, any tributary station waiting to be polled or selected.

passive threat:
A threat of disclosure of information without changing the state of a data processing system; for example, a threat that would result in obtaining sensitive information through the interception of data transmission.

passive vocabulary:
Synonym for recognition vocabulary.

passive wiretapping:
Wiretapping limited to obtaining data.

pass key:
Synonym for privacy key.

A character string that is used as authentication information.

Password Authentication Protocol (PAP):
A protocol providing means to authenticate the name and password of a user.

password-change interval:
The duration of a password's validity.

password security:
The prevention of unauthorized use of a system, device, or program by checking user passwords.

password-selection controls:
Restrictions on users' selection of their own passwords.

(1) A direct modification of an object module, or a loaded program without assembling or compiling anew from the source program. (2) To make a patch.

A sequence of branches that connects two nodes in a network, using each branch only once. A path may consist of only one branch. More than one path may exist between any two nodes.

In artificial intelligence, a set of features and their relationships used to recognize an entity within a given context. These features could include a geometrical shape, a sound, a picture, a signal, or written text.

pattern description language:
A language that provides the structural description of patterns in an image in terms of pattern primitives and their combination.

pattern matching:
In artificial intelligence, the identification of a pattern by comparing it with a predetermined set of patterns and by choosing the closest one according to given criteria. Synonymous with filtering (in artificial intelligence).

pattern recognition:
The identification of shapes, forms, or configurations, by automatic means.

pattern-sensitive fault:
A fault that appears in response to some particular pattern of data.

pattern training:
Synonym for interactive training.

pause instruction:
An instruction that specifies the temporary suspension of the execution of a program; a pause instruction is usually not an exit.

personal computer.

protocol control information.

Personal Computer Memory Card International Association.

PCMCIA card:
A small and flat electronic card that can be connected to a portable computer for communications, multimedia, memory or other purposes and conforming to PCMCIA specifications. PCMCIA cards are divided into Type I, Type II, and Type III.

print contrast signal, personal communications services.

physical delivery.

physical delivery access unit.

page description language.

P-DOW disk:
A type of optical disk that provides for a part of the disk surface to be pre-recorded and reproduced by stamping or other means without recourse to the magneto-optical effect. All parts that are not pre-recorded provide for data to meet requirements for a direct overwrite disk.

physical delivery system.

protocol data unit.

peer entities:
Entities in the same or different open systems that are in the same layer.

peer-entity authentication:
In OSI architecture, the corroboration that a peer entity in an association is the one that it claims to be.

peer-to-peer network:
A computer network that contains only equivalent nodes with respect to their capability of control or operation.

An older term for picture cell, a monochrome version of what is now more commonly called pixel.

The unauthorized access to a data processing system.

penetration testing:
Examining the functions of a data processing systems to find a means of circumventing computer security.

pen plotter:
A plotter that uses pens for producing hard copy.

pen scanner:
A small hand-held scanner allowing its user to scan items, such as bar codes or lines of text.

percentage function:
The function that automatically multiplies two entered numbers, one of which is understood to be a percentage, and divides the results by one hundred.

perception medium:
Medium through which data are perceived by a user; for example: sound as perceived by a human ear; graphics as perceived by a human eye. The perception medium refers to the nature of information as perceived and processed by a human.

An artificial neural network consisting of one artificial neuron, with a binary output which is determined by applying a monotonic function to a linear combination of the input values and with error-correction learning. The perceptron forms two decision regions separated by a hyperplane. For binary inputs, the perceptron cannot implement the nonequivalence operation (EXCLUSIVE OR, XOR).

perfection image:
A digital image giving an impression of reality. Synonymous with ideal image.

perforated tape:
A tape on which a pattern of holes or cuts is used to represent data.

perform statement:
In COBOL, a compound statement that explicitly specifies transfer of control to one or more procedures and the return of control implicitly whenever execution of the specified procedure is completed. The perform statement is also used to control execution of one or more unconditional statements which are within its scope..

peripheral equipment:
Any device that is controlled by and can communicate with a computer; for example: input/output units, external storage.

peripheral node:
Synonym for end node.

peripheral unit:
Synonym for peripheral equipment.

permanent storage:
Storage that is nonerasable.

permissible action:
In a conceptual procedural language, an action conforming to specified rules or constraints that changes a presumably consistent collection of sentences into a consistent one or makes known a consistent one present in the information base or conceptual schema.

The measure of the roundness of a region. Peround is computed as the square of the perimeter divided by the area.

personal communications services (PCS):
An evolving service that incorporates both the concepts of
  1. terminal mobility, which allows subscribers, via their terminals, to originate and receive calls as they travel nationwide and
  2. personal mobility, which is achieved through the use of intelligent switching networks and common channel signaling, and which allows subscribers to obtain consistent service (e.g., digital voice, voice mail, fax, or paging), and billing information regardless of their physical location in the network.
Contrast with Universal Personal Telecommunications.

personal computer (PC):
A microcomputer primarily intended for standalone use by an individual.

personal name:
An attribute or identifier of a unique designation of a person relative to the entity denoted by another attribute, e.g., an organization name. Components of a personal name are for example: A common name or a personal name is required in an O/R address. (Figure 65 - Selected O/R address attributes). (Figure 66 - Examples of O/R addresses).

A publicly available implementation of a public-key encryption system using no trusted third party. PGP is the abbreviation for Pretty Good Privacy.

phase change optical disk:
A WORM or rewritable optical disk providing for data to be written onto the optical disk by causing phase transitions between amorphous and crystalline states of the recording layer, and read using the reflection difference between the two states.

phase coherent frequency shift keying:
Frequency shift keying in which the predetermined frequencies are whole multiples of the bit rate and transitions between these frequencies are made at zero crossings of the carrier waveform. Synonymous with phase-coherent FSK.

phase coherent FSK:
Synonym for phase coherent frequency shift keying.

phase-continuous frequency shift keying:
Frequency shift keying in which the transition between the predetermined frequencies is accomplished by a change of frequency, in such a way that there is no phase shift at the transition. Phase-continuous frequency shift keying may be contrasted with the discontinuous replacement of one frequency by another, such as might be accomplished by a switch. Synonymous with phase-continuous FSK.

phase-continuous FSK:
Synonym for phase-continuous frequency shift keying.

phase encoding:
Encoding in which the phase of the wave is used to encode digital data; for example, Manchester encoding.

phase jitter:
Jitter expressed as a fraction of the significant interval.

phase modulation (PM):
A form of angle modulation in which the phase angle of a carrier is caused to depart from its reference value by an amount proportional to the instantaneous value of the modulating function.

phase modulation recording:
Recording in which data is encoded in the phase of the recorded signal. (Figure 48 - Phase modulation recording).

phase shift keying (PSK):
Modulation in which a modulating digital signal varies the phase of the output signal among a fixed number of predetermined values. (Figure 49 - Phase shift keying).

Programmer's Hierarchical Interactive Graphics System.

The smallest recognizable unit of speech in a given audible language.

Phong shading:
The smooth shading of a closed, multisided area by interpolation of surface normal vectors across a polygon span rather than interpolating the intensity. Contrast with Gouraud shading. (Figure 32 - Gouraud and Phong shading).

Synonym for phototypesetter.

A nonimpact printer that creates characters through photography. Synonymous with photocomposer.

(1) Pertaining to actual implementation or location as opposed to conceptual content or meaning. (2) Pertaining to the representation and storage of data on a medium such as magnetic disk, or to a description of data that depends on physical factors such as length of data elements, records, or pointers. Contrast with logical.

physical access control:
The use of physical mechanisms to provide access control; for example, keeping a computer in a locked room.

physical data structure:
The form in which data are stored on a medium.

physical delivery (PD):
The delivery of a message in physical form. The physical form may be a letter.

physical delivery access unit (PDAU):
An access unit for physical delivery; for example: a printer.

physical delivery system (PDS):
A system that performs physical delivery; for example: the postal system.

physical layer:
In OSI, the layer that provides the mechanical, electrical, functional, and procedural means to establish, maintain and release physical connections for transfer of bits over a transmission medium. (Figure 47 - The Open Systems Interconnection Reference Model).

physical level:
A level of consideration at which all aspects deal with the physical representation of data structures and with mapping them on corresponding storage organizations and their access operations in a data processing system.

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