P A| B| C| D| E| F| G| H| I| J| K| L| M| N| O| P| Q| R| S| T| U| V| W| X| Y| Z| Numerical Listing| PABX (Private Automatic Branch Exchange) Originally called a PBX. A telephone switch located on a customer’s premises that primarily establishes voice-grade circuits (over tie lines to a telephone company central office) between individual users and the public-switched telephone network. The PBX also provides switching within the customer premises local area, and usually offers numerous enhanced features, including least-cost routing and call-detail recording. Packet An information block identified by a label at Layer 3 of the International Standards Organization reference model for Open Systems Interconnection. It is a collection of bits that contain both control information and data, and the basic unit of transmission in a packet-switched network. Control information is carried in the packet, along with the data, to provide for such functions as addressing sequence, flow control and error control at each of several protocol levels. A packet can be of fixed or variable length, but generally has a specified maximum length. Packet Format The exact order and size of a packet’s various control and information fields, including header, address and data fields. Packet Overhead A measure of the ratio of the total packet bits occupied by control information to the number of bits of data; usually expressed as a percent. Packet Switching A technique in which a message is broken into smaller units called packets, which may be individually addressed and routed through the network, possibly using several different routes. The receiving-end node ascertains that all packets are received and in the proper sequence before forwarding the complete message to the addressee. PAD (Packet Assembler/Disassembler) An interface device that buffers data sent to and from character mode devices, and assembles and disassembles the packets needed for X.25 operation. Parallel Processing The solution of a single problem across more than one processor. Little parallel processing is done today outside of research laboratories, because it is difficult to decompose tasks into independent parts, and the compiler technology does not yet exist that will extensively parallelize applications code. TOP OF PAGE Parallel Systems Hardware configurations having nine or fewer central processing units. Compare with highly parallel systems and massively parallel systems. PBX (Private Branch Exchange) A telephone switch located on a customer’s premises that primarily establishes voice-grade circuits (over tie lines to a telephone company central office) between individual users and the public-switched telephone network. The PBX also provides switching within the customer premises local area, and usually offers numerous enhanced features, including least-cost routing and call-detail recording. PC ALL-IN-1 A Digital Equipment Corp. product that lets the user interface and other input/output-intensive portions of ALL-IN-1 reside on the PC. PC-DOS The operating system that IBM supplies with its personal computers. PCB (Printed Circuit Board) A flat board composed of chips and electronic components, that is made from fiberglass or plastic and interconnects components via copper pathways. The primary PCB in a system is called a system board or motherboard, while smaller ones that plug into the slots in the main board are called boards or cards. PCM (Plug-Compatible Manufacturer) A hardware vendor whose products are direct replacements for the products of a computer systems manufacturer. Initially PCMs provided peripherals that were "plug-for-plug" compatible with IBM peripherals, but the PCM industry has since grown to include IBM-compatible mainframes and peripherals for other vendors’ systems. TOP OF PAGE PCM (Pulse Code Modulation) A form of modulation in which the modulating signal is sampled, and the sample quantized and coded. It is the standard technique in telecommunications transmission. PCMCIA (Personal Computer Memory Card International Association) A nonprofit trade association founded in 1989 to standardize the PC card. PCMCIA cards are removable modules that can hold memory, fax/modems, radio transceivers, network adapters, solid state disks or hard disks. PCMCIA cards are 85.6 mm long by 54 mm wide (3.37 inches x 2.126 inches) and use a 68-pin connector. The original Type I card is 3.3 mm thick and is now used for memory in personal digital assistants and other lightweight applications. PCN (Personal Communications Network) PCN is a highly functional technology that operates like digital cellular service, except that it uses cells with a much smaller radius, 600 feet. PCS (Personal Communications Services) A new, lower-powered, higher-frequency competitive technology to cellular. Whereas cellular typically operates in the 800-900 MHz range, PCS operates in the 1.5 to 1.8 Mhz range. PDA (Personal Digital Assistant) A pen-based, wireless transmitter that serves as an organizer, electronic book or note taker that features cellular service or desktop system. PDES (Product Data Exchange using STEP) A United States organizational activity that supports the development and implementation of STEP data exchange. TOP OF PAGE PDES (Product Data Exchange Specification) A standard format for the exchange of data between advanced computer-aided design and computer-aided manufacturing programs. It describes a complete product, including the geometric aspects of the images, manufacturing features, tolerance specifications, material properties and finish specifications. PDF (Portable Document Format) The title format used by Adobe Systems' Acrobat document exchange system. PDN (Public Data Network) A shared-use X.25 packet-switched network operated by a carrier. PDNs may offer value-added services at a reduced cost because of communications resource sharing and usually provide increased reliability due to built-in redundancy. Peer Networking LAN Manager: An application programming interface (API) is available at the midrange system enabling program-to-program communications with OS/2 programs using the Named Pipes API and LAN Manager protocols. MS-Net: An API is available at the midrange system enabling program-to-program communications with MS-DOS programs using the NetBIOS API and MS-Net protocols. Proprietary: An API is available at both the midrange system and Macintosh, enabling program-to-program communications using the midrange system’s native peer networking protocols. Peer Process — APPC LU 6.2. support. Midrange system peer communications support using IBM’s Advanced Program-to-Program Communications protocols. Peer Process — CPI-C API Support is provided for applications that use IBM’s Common Programming Interface for Communications for peer-to-peer communications. Peer-to-Peer Access to application-to-application facilities between network-attached midrange systems of the same supplier. Performance Monitoring and Tuning Tools A facility that enables users to monitor midrange system performance, identify system and application performance bottlenecks and set optimal performance-tuning parameters. TOP OF PAGE Permanent Virtual Circuit A logical circuit that is set up for point-to-point communications between two data terminal equipment elements without the need for call setup or tear-down. Personal Services A family of program products, one for each office system machine (i.e., PS/CICS, PS/TSO, PS/36, PS/38 and PS/PC) that extends the IBM office network architecture to that environment. Personal Services/X (where X is 36, 38, etc.) provides document exchange capabilities with the other family members, as well as calendar management and other office administrative function. PERT (Program Evaluation and Review Technique) A management tool for graphically displaying projected tasks and milestones, schedules and discrepancies among tasks. PHIGS (Programmers Hierarchical Interactive Graphics Standard) PHIGS is a graphics system and language used to create 2-D and 3-D images that interface between the application program and the device independent graphics subsystem. Graphics objects are managed in a hierarchical manner so that a complete assembly can be specified with all of its subassemblies. High-performance workstations and host processing are required to handle the standard. Physical Layer Within the Open Systems Interconnection model, the lowest level of network processing, below the link layer, that is concerned with the electrical, mechanical and handshaking procedures over the interface that connects a device to a transmission medium (e.g., RS-232-C). PIM (Personal Information Manager) Software that organizes and manages random information for fast retrieval on a daily basis. It provides a combination of features, including telephone list with automatic dialing, calendar, scheduler and tickler. PIR (Protocol Independent Routing) A method in which routing decisions are made with no reference to the protocol in use. Protocol-independent routers have the functionality of protocol-specific routers, but can also route nonroutable protocols. Pixel (Picture Element) The smallest resolvable dot in an image display. TOP OF PAGE Pixtext Image-oriented, document management product from Excalibur Technologies of Albuquerque, N.M. PL/SQL (Programming Language/Structured Query Language) One of the two deliverables of Oracle Systems Transaction Processing Option (TPO). It is a 3GL-level extension of SQL that groups SQL statements for transmission across the tools/database management system interface or across a network. PL/SQL must be used to take advantage of the Oracle version 6 performance enhancements. PM (Presentation Manager) The OS/2 graphical user interface, which includes windowing, graphics, standards for the keyboard interface, and editors for icons and fonts. It is the first manifestation of IBM’s User Interface Architecture, and is consistent with the common user access component of Systems Application Architecture. PM/X (Presentation Manager/X) A graphical user interface product developed by Hewlett-Packard and Microsoft that provides an OS/2 Presentation Manager-compatible application programming interface on Unix workstations, which coexists with X Windows. POMS (Process Operations Management System) An IBM- and customer-supported initiative to link MRP II applications running on AS/400 minicomputers and shop-floor data collection systems running on PS/2 computers. It is not an IBM product, although IBM funded its development. IBM, however, has exclusive marketing rights. Port The entrance or physical access point to a computer, multiplexer, device, or network where signals may be supplied, extracted, or observed. Ported Proprietary Refers to a system that is a compliant implementation of an evolving set of proprietary or vendor-neutral specifications (or both) for interfaces, services, protocols and formats. These specifications let a user configure and operate a system, its applications and its components only with other equally compliant implementations available from the same vendor or with licensed implementations from different vendors. TOP OF PAGE POS (Point of Sale) Point of sale systems use personal computers or specialized terminals in combination with cash registers, optical scanners that read product identification, and/or magnetic stripe readers for reading credit cards that capture and record data at the time of transaction. Point of sale systems are usually on-line to a central computer for credit checking and inventory updating. Alternatively they may be independent systems that store daily transactions until they can be transmitted to the central system for processing. Posix (Portable Operating System for Computer Environments) A Unix-based standard developed by the Institute of Electrical and Electronics Engineers POSIX committee. In August 1988, the committee officially released the first installment of the standard (1003.1), a core set of system calls. Other pieces, such as real-time extensions, are also under consideration by various subcommittees. POSIX has been adopted as a Federal Information Processing Standard (FIPS), and is included in the Open Software Foundation’s and X/Open’s basic specifications. Posix 1003.1 Compliance Operating system compliance with the Institute of Electrical and Electronics Engineers Posix 1003.1 system services standard. PostScript Printer Support Support for the printing of compound document information, including "rich text," on PostScript printers. POWER (Performance Optimized with Enhanced RISC) IBM’s proprietary reduced instruction set computer processor technology used in the RS/6000 and selectively licensed to other suppliers, including Motorola. Powerfail Restart Automatic restart initiation upon restoration of power after a power failure. PQS (Parallel Query System) A product announced by IBM in April 1994 that uses CMOS technology and provides parallelization of DB2 (read-only) queries. PR/SM (Processor Resources/Systems Manager) IBM’s logical partitioning facility that allows the computer architecture to be separated from its physical implementation to provide a logical organization of resources that allows multiple operating systems (or copies of the same system) to run on one physical central processing unit or complex. TOP OF PAGE Precision Architecture Hewlett-Packard’s reduced instruction set computer-based processor architecture, the basis for its desktop to mainframe processor products. It serves as a single design point to consolidate HP’s three computer families: HP 9000/800 Unix multiuser system and servers; HP 9000/700 Unix servers and workstations; and HP 3000 commercial MPE/XL multiuser system and servers. Predicate A clause within a Structured Query Language statement (query) that specifies a constraint that the selected data (rows) must satisfy. Predicate Transitive Closure The practice of adding semantically redundant predicates to a Structured Query Language statement (query) to help the optimizer perform better. This can be done by application programmers or by the optimizer itself. Presentation Layer In the Open Systems Interconnection model, that layer of processing that provides services to the application layer, enabling it to interpret the data exchanged, as well as to structure data messages to be transmitted in a specific display and control format. Presentation Manager The OS/2 graphical user interface, which includes windowing, graphics, standards for the keyboard interface, and editors for icons and fonts. It is the first manifestation of IBM’s User Interface Architecture, and is consistent with the common user access component of Systems Application Architecture. PRI (Primary Rate Interface) An Integrated Services Digital Network (ISDN) interface that connects PBXs to the network at the North American 1.544-Mbps T1 rate. It is electrically identical to the ISDN basic rate interface. North American standards for this interface specify 23 64-Kbps B, or bearer, channels, plus one 64-Kbps D, or delta, channel. Thus, it is also referred to as 23B+D. European standards call for 30B+D. PRISM (Parallel Reduced Instruction Set Multiprocessor) A reduced instruction set computer architecture developed by Apollo for its high-end workstation products. TOP OF PAGE Process An interconnected network of activities that begins at the specification of a requirement for a product or service and terminates with the acceptance of consideration for providing the product or service. Process Control The regulation of variables that influence and/or control the conduct of a process so that a specified quality and quantity of product are obtained. Process Coordination The class of applications that exploits work-flow technology. Product Data Management (PDM) A set of technologies and capabilities for comprehensively managing design intent and product development processes across the enterprise. PROFS (Professional Office System) Office systems facilities for the Virtual Machine (VM) environment. The E-mail function is particularly strong and is widely used within IBM. The user interface, however, is not oriented toward novice users. PROFS began as a program RPQ (request for quotation) and, like VM itself, was a "stepchild" for some time. PROFS Document Exchange A facility to exchange documents to or from the midrange system with IBM’s Professional Office System. PROFS document content can be compatible with DISOSS (Document Content Architecture), although distribution and exchange of documents or notes requires a different approach. TOP OF PAGE Programmable Logic Controller A programmable logic controller is a specialized industrial computer used to programmatically control production and process operations by interfacing software control strategies to input/output devices. Protected Mode A mode of the Intel 80286, 80386 and 80486 microprocessors with hardware memory protection, which is important for multitasking and for escaping the 640K memory barrier. Protocol A set of procedures for establishing and controlling data transmission. Examples include IBM’s BSC (Binary Synchronous Communications) and SDLC (Synchronous Data Link Control) protocols. PSTN (Public Switched Telephone Network) A worldwide voice telephone network. PTOCA (Presentation Text Object Content Architecture) Describes character data, position controls and attributes that represent a formatted text presentation. PTS (Parallel Transaction Server) A product announced by IBM in April 1994 that introduces CMOS-based parallelism to Information Management System/Database Manager applications. PTT (Postal Telegraph and Telephone) A term formerly used to refer to the agency responsible for postal, telegraph and telephone services at a governmental level. PU (Physical Unit) A physical device used in IBM Systems Network Architecture (SNA) communications; includes the software in an SNA node controlling the node’s communications hardware. PU is synonymous with "node type" within SNA. PU 2 devices are intelligent cluster controllers/terminals. A PU 2.1 node enables local user ports to communicate without going through a host node’s services. TOP OF PAGE PVC (Permanent Virtual Circuit) A virtual circuit established through manual or protocol interaction rather than via a call establishment sequence. Comments? Questions? Entire contents Copyright © 1997, 1998 by Gartner Group, Inc. All rights reserved. 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