P

P               Positive Flag. The processor-status flag that indicates a
                positive result.
P3              Primavera Project Planner.
PA              Point-of-Attachment.
PABX            See PBX.
PACE            Processing And Control Element.
PACX  		Private Automatic Computer eXchange (eg data switch).
PAD             Packet Assembler/Dissembler. A device used with an X.25 
                packet switching network to allow character-mode terminals to 
                communicate with a packet-mode device, such as a computer.
PAL             Phase Alternation Line.
PAM             Phase Amplitude Modulation.
PARC            Palo Alto Research Center.
PARP            Proxy Address Resolution Protocol.
PASM            PArtitionable Single Instruction stream Multiple Data stream 
                Multiple Instruction stream Multiple Data stream. See also 
                SIMD, MIMD. Used for parallel image understanding.
PAX             Processor Array eXperiment. A rectangular array of 128 
                processing units.
PB              Page Buffer.
PBX/PABX        Private Branch eXchange or Private Automated Branch eXchange.
                A switching network for voice or data.
PC              Personal computer. A single-user computer with a base price
                of less than about $5000 (e.g. the IBM PC, the IBM PS/2, the
                Apple Macintosh). See also IBM PC, IBM PC AT.
PC              Program Counter. The register in a CPU that points to the
                next instruction to be executed; also called an instruction
                pointer or instruction counter.
PCA		Policy Certification Authority.
PCB             Printed Circuit Board. A thin, nonconductive board that holds
                the components of a circuit. The manufacturer laminates the
                board with conductive material and uses the etching process
                to remove unwanted material, leaving only the conductive
                wires (traces) that become the circuit; the integrated
                circuits and other components are then firmly attached to the
                board and the pins soldered to the traces.
PCB             Program Communication Block. A type 1 view in IMS is a
                subhierarchy and is defined by means of a PCB.
PCBC		Plain-and-Cipher Block Chaining.
PC DOS          Personal Computer Disk Operating System. The IBM's operating
                system on PC.
PCI             Peripheral Component Interconnect.
PCL             Printer Control Language.
PCLSP           PC Lan Support Program. The IBM PCLSP was developed to
                replace the NETBEUI when the PS/2 family of PCs was
                introduced. It functions much the same manner as NETBEUI but
                is implemented as a set of device drivers rather than a
                memory-resident program.
PCM             Package Command Manager.
PCM             Plug Compatible Module.
PCM             Pulse Code Modulation. It refers to a specific encoding
                format for sound samples. This format is currently used for
                WAV files. See also WAV.
PCMCIA		Personal Computer Memory Card International Association.
PCR             Parent-Child Relationship. A PCR type is a 1:N relationship
                between two record types. The record type on the 1-side is
                called the parent record type, and the one on the N-side is
                called the child-record type of the PCR type.
PCR             Pen Character Recognition.
PCS             Personal Communications Services.
PCS             Personal Conferencing Specification.
PCWG            Personal Conferencing Work Group.
PCX		PC Paintbrush picture. File extension.
PDA             Personal Digital Assistant.
PDB             Physical DataBase. A stored hierarchy in IMS is called a PDB.
PDES            Product Data Exchange using STEP. The PDES is a
                standardization of the product data for exchange puposes
                across vendors, designers, and manufacturers.
PDF             Package Definition File.
PDF             Portable Document Format. PDF is Adobe Acrobat's document 
                description format.
PDL             Page-Description Language.
PDN             Public Data Network.
PDP             Programmed Data Processor. See PDP-10, PDP-11, PDP-8.
PDP-10          In the early 1970s DEC introduced the PDP-10 model KL-10, a
                two-processor shared-memory computer that could be configured
                as either a master-slave or symmetric system.
PDP-11          An 16-bit minicomputer introduced by Digital Equipment
                Corporation (circa 1970).
PDP-8           An 8-bit minicomputer introduced by Digital Equipment
                Corporation (circa 1965).
PDS             Processor Direct Slot.
PDT             Performance Diagnostic Tool.
PDU             Protocol Data Unit. The sequence of contiguous octets
                delivered as a unit from or to the MAC sublayer. A valid LLC
                PDU is at least 3 octets in length and contains two address
                fields and a control field. A PDU may or may not include an
                information field in addition.
PE              Phase Encoding.
PE              Presentation Entity.
PE              Processing Element. A processing node of a processor array,
                multiprocessor or dataflow machine.
PEM		Privacy Enhanced Mail.
Perfect Club Suite
                Perfect stands for PERFormance Evaluation for Cost-effective
                Transformation. A suit of 13 scaled-down, real-world programs,
                taken from the sciences, for measuring the performances of
                computers.
PERL            Practical Extraction and Reporting Language.
PERT            Program Evaluation and Review Technique.
PES		Proposed Encryption Standard.
PET             Personal Electronic Transactor computer. An early personal
                computer, introduced in 1977 by Commodore Business Machines.
PFC             Parallel Fortran Converter.
PFG             Plant and Fractal Generator.
PGA             Pin Grid Array. An integrated-circuit-packaging technology
                where the pins, which project from the bottom of the chip,
                are arranged in concentric squares.
PGC             Program Group Control.
PGP		Pretty Good Privacy.
PGT             PaGe Table.
PIA             Peripheral Interface Adapter.
PICU            Priority Interrupt Control Unit.
PIM             Personal Information Manager.
PIM-D           Parallel Inference Machine based on the Dataflow model.
PIN		Personal Identification Number.
PINE            Pine Is No-longer Elm.
PLATO-UK        PLAnt TOxins-United Kingdom.
PLCL            Phase-Locked Control Loop.
PLL             Phase-Locked Loop.
PLN             Probabilistic Logic Node.
PLS             Physical Layer Signaling.
PM              Preventive Maintenance.
PMI             Physical Medium Attachment.
PMOS            P-channel Metal-Oxide Semiconductor.
P-NNI           Private Network-to-Network Interface.
POP             Point Of Presence.
POP3		Post Office Protocol V3.
POSE            Portable Operating System Extention.
POST            Power-On Self-Test. A brief examination of the system's
                functionality performed each time the system is turned on.
POTS            Plain Old Telephone System.
PPI             Programmable Parallel Interface. A programmable I/O interface 
                that sends and receives all of the bits of a word at the same
                time, as opposed to one that operates in bit-serial fashion, 
                e.g. sequentially on the bits of a word. See also 8255A.
PPP             Point-to-Point Protocol.
PPSDN           Public Packet-Switched Data Network.
PPU             Peripheral Processing Unit. An intelligent I/O processor. One
                that has sufficient local memory to hold I/O programs and
                buffer I/O operations, and has a relatively complex 
                instruction-set.
PQFP            Plastic Quad Flatpack Package. An integrated-circuit packaging
                technology in which the pins, which are soldered directly to
                the traces of a printed-circuit board, project from all four
                sides of a square integrated circuit.
PRAM            Parallel Random Access Memory.
PReP            Powerpc Reference Platform.
PRI             Primary Rate Interface.
PRNG		Pseudo-Random Number Generator.
PROM            Programmable Read Only Memory.
PRR             Pulse Repitition Rate.
PS              Processor Sharing.
PS              Programmable Switch.
PS/2            See IBM PS/2.
PSAP            Presentation Service Access Point.
PSB             Program Specification Block.
PSDN            Packet-Switched Data Network. A communication network that 
                has been set up and is controlled by a public 
                telecommunications authority for the exchange of data.
PSK             Phase-Shift Keying. A modulation technique used to convert 
                binary data into an analogue form comprising a single 
                sinusoidal frequency signal with a phase that varies 
                according to the data being transmitted.
PSN             Packet-Switching Networks. Packet-switching is an efficient
                method of transmitting large volumes of data between widely
                separated processing sites.
PSOUP           Primordial SOUP.
PSP             Program Segment Prefix. The Program Segment Prefix is a
                256-byte data area prepended to a program when it is loaded.
                It contains the command line that the program was invoked
                with, and a variety of housekeeping information for DOS.
PSTN            Public-Switched Telephone Network. This is the term used to 
                describe the (analogue) telephone network.
PSW             Program Status Word. The word in a CPU that holds the
                processor-status bits and often additional information, such
                as protection key, interrupt-mask register, interrupt-code
                register and program counter.
PTF             Problem Trouble Fix.
PTP             Packet Transport Protocol.
PTP             Paper Tape Punch.
PTRP            Paper Tape Reader-Switch.
PTT             Post Telephone and Telecommunications. The administrative 
                authority that controls all the postal and public 
                telecommunications networks and services in a country.
PTX             Performance ToolboX.
PU              Physical Unit.
PUC             Public Utilities Commission.
PV              Physical Volume.
PVC             Permanent Virtual Circuit.
PVM             Paralel Virtual Machine. It is a software package for 
                utilizing a heterogeneous network of computers as a single 
                computational resource.
PVS             Power Visualization System. The IBM PVS consists of up to 32 
                i860 processors running at 40 MHz and provided with up to 
                2 GBytes of shared memory by a multistage switching network.
PW              Pulse Width.
PWORD           Penta-WORD. Six bytes.  Used to hold an 80386 protected-mode
                "far" address, consisting of a segment selector and a 32-bit
                offset, or a Turbo Pascal "real" variable. See also DWORD,
                QWORD.

Q

QAM             Quadrature Amplitude Modulation.
QBE             Query By Example. QBE is a user-friendly relational query
                language that was developed at IBM Research. QBE is available
                as an IBM commercial product as part of the QMF interface
                option DB2.
QCDPAX          Quantum ChromoDynamics Processor Array eXperiment. The QCDPAX 
                is a more recent machine intended primarily for quantum 
                chromodynamics computations.
QFP             Quad Flat Package.
QIC             Quarter-Inch Cartridge.
QLLC            Qualified Logical Link Control.
QMF             Query Management Facility. See also QBE.
QPSX            Queued Packet and Synchronous eXchange. QPSX is a sole MAN
                standard. See also DQDB.
QWORD           Quad-WORD. Eight bytes.  See also DWORD, PWORD.
