P
* Packet
* Packet Buffer
* Packet Switching
* PAD: Packet Assembler / Disassembler
* Page Down Key
* Page Printer
* Page Up Key
* Page-White Display
* PAL: Phase Alternating Line
* Parallel Interface
* Parallel Port
* Partitions
* Passive-Matrix Display
* Patch Cord
* Patch Panel
* PCB: Printed Circuit Board
* PCI Express
* PCI: Peripheral Component Interconnect
* PCI-X: PCI Extended
* PCL: Printer Control Language
* PCMCIA: Personal Computer Memory Card International Association
* PDA: Personal Digital Assistant
* PDP-10: Programmed Data Processor model 10
* PDP-11: Programmed Data Processor model 11
* Peripheral
* Peripheral Equipment
* Personal Computer
* Petaflop
* PGA: Pin Grid Array
* Photo Printer
* Photo Scanner
* PIA: Peripheral Interface Adapter
* PIC: Personal Internet Communicator
* PID: Proportional Integral Derivative
* Pincushion Distortion
* Pinout
* Pipeline Burst Cache
* Plasma Display
* Platter
* PLCC: Plastic Leaded Chip Carrier
* PLD: Programmable Logic Device
* PLED: Polymer (polymeric) Light-Emitting Diode
* Plug
* PMOS
* PnP: Plug and Play
* Pointing Device
* Polyfont Recognition
* Port
* Port Mapped I/O
* Port Switcing Hub
* Posted Write-Through
* PowerPC
* PPGA: Plastic Pin Grid Array
* PPI: Pixels Per Inch
* PRAM: Parameter RAM
* Primary Cache
* Primary Storage
* Print Server
* Printer
* Printer Driver
* Printer Engine
* Printer Spooling
* Processor
* PROM: Programmable Read-Only Memory
* Protocol Stack
* Proxy Cache
* Proxy Gateway
* Proxy Server
* PS/2 Port
* Punchdown Block
* PWM: Pulse Width Modulation
packet
Packet, maybe called datagram in some cases, is a unit of a message transmitted over a packet-switching network. Data is broken up into packets for sending over a packet switching network. Each packet has a header containing its source and destination, a block of data content, and an error-checking code. All the data packets related to a message may not take the same route to get to their destination; they are reassembled once they have arrived.
packet buffer
Packet buffer is the memory space reserved for storing a packet awaiting transmission or for storing a received packet. Packet buffer is set aside specifically for either storing a packet that is awaiting transmission over a network or storing a packet that has been received over a network. The memory space is either located in the network interface card or in the computer that holds the card.
packet switching
Packet switching refers to the following process: A message may be broken down into multiple packets and each packet is transmitted individually and can even follow different routes to its final destination. Once all the packets forming a message arrive at the destination, they are recompiled into the original message.
PAD: packet assembler / disassembler
Packet switching refers to the following process: A message may be broken down into multiple packets and each packet is transmitted individually and can even follow different routes to its final destination. Once all the packets forming a message arrive at the destination, they are recompiled into the original message.
Page Down key
Page Down key, or Pg Dn, is a key on PC and Macintosh keyboards to move the cursor down to the end of the page on the screen. Its meaning may slightly differ from one program to another.
page printer
Page printer is a printer that processes an entire page at one time, in contrast to line printers. All laser and ink-jet printers are page printers.
Page Up key
Pave Up Key, often abbreviated Pg Up, is a key PC and Macintosh keyboards to move the cursor up to the top of a page on a screen. Its meaning may differ from one program to another.
page-white display
Page-white display is a special type of LCD display screen that uses supertwist technology to produce a high contrast between the foreground and background.
PAL: Phase Alternating Line
Phase Alternating Line (PAL) is the television standard popular in Europe and Asia. The United States uses a different standard, NTSC. PAL delivers 625 lines at 50 half-frames per second while NTSC delivers 525 lines of resolution at 60 half-frames per second. Many video adapters that enable computer monitors to be used as television screens support both NTSC and PAL signals.
parallel interface
Parallel interface, used to connect the printer on a PC, is a port that transmits a number of bits at a time by means of multiple parallel channels. A common parallel interface used in personal computers has 36 channels; eight channels are used to transfer a byte of data at one time, and the other channels are for addressing, error correction, and other control signals.
parallel port
Parallel port, also called a female connector, is a socket on a computer for transmitting data in parallel, or more than one bit at a time. There may be 8, 16, or 36 channels; each channel carries one bit of information, so eight channels would be used to transmit one eight-bit byte at a time. Not all the channels are used for data; some may be used for control signals. Parallel port connects a computer with an external device such as a printer. Most personal computers have both a parallel port and at least one serial port. On PCs, the parallel port uses a 25-pin connector (type DB-25) and is used to connect printers, computers and other devices that need relatively high bandwidth.
Partitions
Partitions refers to the divisions of the total physical hard disk space into a few logic areas.
passive-matrix display
Passive-matrix display is type of flat panel video display that uses a series of criss-crossed wires with an LCD element at each intersection to produce a picture. Each element represents a pixel and can either allow light to pass or not. In contrast, an active-matrix display has a single transistor to represent each picture element (pixel). Passive-matrix displays are cheaper to produce but can't produce as sharp a picture as an active-matrix display.
patch cord
Patch cord, also known as a patch cable, is a short piece of copper wire or fiber optic cable. Patch cord is used to connect ports in patch panels or in expansion boards and systems that are in close proximity.
patch panel
Patch panel is a panel of network ports contained together, usually within a telecommunications closet, that connects incoming and outgoing lines of a LAN or other communication, electronic or electrical system. The patch panel allows easy access to all cable and ground line conductors. Conductor functions can be interchanged or checked rapidly for continuity, insulation, or quality of signal brought to the surface. Also, it provides easy access to output of surface panels.
PCB: Printed circuit board
Printed Circuit Board (PCB) is a thin plate on which chips and other electronic components are placed. A printed circuit board consists of "etched conductors" attached to a sheet of insulator. The conductive "etched conductors" are called "traces" or "tracks". The insulator is called the substrate.
PCI Express
PCI Express, a new generation of PCI, is an I/O interconnect bus standard that expands on and doubles the data transfer rates of original PCI. PCI Express is a two-way, serial connection that carries data in packets along two pairs of point-to-point data lanes, compared to the single parallel data bus of traditional PCI that routes data at a set rate. Initial bit rates for PCI Express reach 2.5Gb/s per lane direction, which equates to data transfer rates of approximately 200MB/s.
PCI: Peripheral Component Interconnect
PCI Express, a new generation of PCI, is an I/O interconnect bus standard that expands on and doubles the data transfer rates of original PCI. PCI Express is a two-way, serial connection that carries data in packets along two pairs of point-to-point data lanes, compared to the single parallel data bus of traditional PCI that routes data at a set rate. Initial bit rates for PCI Express reach 2.5Gb/s per lane direction, which equates to data transfer rates of approximately 200MB/s.
PCI-X: PCI extended
PCI-X, also known as PCI extended, is an enhanced PCI bus. PCI-X is backward-compatible with existing PCI cards. The technology was developed jointly by IBM, HP, and Compaq. PCI-X doubles the speed and amount of data exchanged between the computer processor and peripherals.
PCL: Printer Control Language
Printer Control Language (PCL) is the page description language (PDL) developed by HP that has become a de facto industry standard. Originally developed for early inkjet printers in 1984, PCL has been released in varying levels for thermal, dot matrix printer, and laser printers. PCL 5 and later versions support a scalable font technology called Intellifont.
PCMCIA: Personal Computer Memory Card International Association
Personal Computer Memory Card International Association (PCMCIA) is an organization consisting of some 500 companies. It has developed a standard for small, credit card-sized devices, called PC Cards. Now, people refers this standard as PCMCIA. Originally designed for adding memory to portable computers, the PCMCIA standard has been expanded several times and is now suitable for many types of devices. There are in fact three types of PCMCIA cards.
PDA: Personal digital assistant
Personal digital assistants (PDAs), also known as or palmtops, are handheld devices that were originally designed as personal organizers, but became much more versatile over the years. A basic PDA usually includes a clock, date book, address book, task list, memo pad, and a simple calculator. One major advantage of using PDAs is their ability to synchronize data with a PC or home computer. PDA can also be used to access to the Internet through wireless communications.
PDP-10: Programmed Data Processor model 10
Programmed Data Processor model 10 (PDP-10) was a computer manufactured by Digital Equipment Corporation (DEC) from the late 1960s on. It was the machine that made time-sharing common; it looms large in hacker folklore because of its adoption in the 1970s by many university computing facilities and research labs, the most notable of which were MIT's AI Lab and Project MAC, Stanford's SAIL, and Carnegie Mellon University.
PDP-11: Programmed Data Processor model 11
Programmed Data Processor model 11 (PDP-11) was a series of 16-bit minicomputers sold by Digital Equipment Corp. in the 1970s and 1980s. The PDP-11 was a successor to DEC's PDP-8 computer in the PDP series of computers. It had several uniquely innovative features, and was easier to program than its predecessors. While well-liked by programmers, it was replaced in the mid-range minicomputer niche by the VAX-11 32-bit extension of the PDP-11. Much of the market for both machines would be taken by personal computers, including the IBM PC and Apple II, and workstations, such as those from Sun Microsystems.
peripheral
Peripheral, or peripheral device, refers to all the I/O devices related with a computer. A peripheral can reside within the same chip as the processor; in which case, it can be called an integrated or on-chip peripheral. It can also be an external device outside the computer such as the keyboard, mouse, printer etc.
Peripheral Equipment
Peripheral Equipment refers to any input/output devices related to a comuputer. Examples of the peripheral equipment include mouse, keyboards and printers.
personal computer
Personal Computer(PC) is a computer designed for use by one person at a time. The term "PC" is also commonly used to describe an "IBM-compatible" personal computer in contrast to an Apple Macintosh computer. In price, personal computers range anywhere from a few hundred dollars to thousands of dollars. All are based on the microprocessor technology that enables manufacturers to put an entire CPU on one chip. Personal computers are used for word processing, accounting, desktop publishing, and for running spreadsheet and database management applications and play games.
petaflop
A petaflop is a theoretical measure of a computer's speed and can be expressed as: A thousand trillion floating point operations per second; A thousand teraflop; 10 to the 15th power floating point operations per second; 2 to the 50th power FLOPS. Today's fastest parallel computing operations are capable of teraflop speeds. A petaflop is the ability of a computer to do one quadrillion floating point operations per second (FLOPS.) A petaflop computer would require a massive number of computers working in parallel on the same problem. Applications might include real-time nuclear magnetic resonance imaging during surgery or even astrophysical simulation.
PGA: Pin Grid Array
Pin Grid Array (PGA) is a type of packaging used for integrated circuits, particularly microprocessors. The integrated circuit (IC) is mounted in a ceramic slab of which one face is covered, or partially covered, in a square array of metal pins. The pins can then be inserted into the holes in a printed circuit board and soldered in place. They are almost always spaced a tenth of an inch (2.54 mm) apart. For a given number of pins, this type of package occupies less space than older types such as the dual in-line package (DIL or DIP). PGA chips are particularly good for chips that have many pins, such as modern microprocessors.
Photo printer
A photo printer, also called snapshot printer, is a computer printer that is specifically designed to print high quality digital photos on photo paper. These printers usually have a very high number of nozzles and are capable of printing droplets as small as 2 picoliters.
photo scanner
Photo scanner is an optical scanner that specialises in scanning photos. Photo scanners usually offer better resolution than conventional scanners. A typical photo scanner is a sheet-fed scanner that can scan 3x5-inch or 4x6-inch photographs at 300 dpi or higher resolution. Some high-end photo scanners can also scan negatives and slides.
PIA: Peripheral Interface Adapter
The Peripheral Interface Adapter (PIA) is a peripheral integrated circuit providing parallel I/O interfacing capability for microprocessor systems. PIA is a specialized interface chip that allows a computer to connect to peripherals such as printers or monitors. The PIA provides two eight-bit ports through which the data passes. Common PIAs include the Motorola MC6820 and MC6821, and the MOS Technology MCS6520, all of which are functionally identical but have slightly different electrical characteristics. The PIA is most commonly packaged in a 40 pin DIP package.
PIC: Personal Internet Communicator
The Personal Internet Communicator (PIC) is designed to provide managed Internet access for people in global, high-growth markets to enhance communications, entertainment, and education opportunities. The PIC is a connecting device; a simple and accessible platform designed to work with existing service provider dial-up or broadband infrastructure that can deliver basic Internet functions such as e-mail, downloads, Web browsing, and more.
PID: Proportional Integral Derivative
A Proportional-Integral-Derivative controller or PID is a standard feedback loop component in industrial control applications. It measures an "output" of a process and controls an "input", with a goal of maintaining the output at a target value, which is called the "setpoint". An example of a PID application is the control of a process temperature, although it can be used to control any measurable variable which can be affected by manipulating some other process variable. For example, it can be used to control pressure, flow rate, chemical composition, force, speed or a number of other variables.
pincushion distortion
Pincushion distortion is a common type of distortion in CRT monitors in which horizontal and vertical lines bend inwards toward the center of the display. The distortion is most noticeable at the edges of the display. Pincushion distortion is a divergence from the rectilinear projection in geometric optics where image magnification increases with increasing distance from the optical axis.
pinout
Pinout is a diagram or table used in electronics to describe how a connector is wired. Each pin of the connector has a purpose which is briefly described in the pinout. The pinout can be shown as a simple table or may include a diagram. It is important to make it clear how to view the diagram, saying if it shows you the backside of the connector (where you attach wires to it) or the "mating face" of the connector. Published pinouts are particularly important when different manufacturers want to interconnect their products using open standards.
pipeline burst cache
Pipeline burst cache is a type of memory cache built into many DRAM controller and chipset designs. The purpose of pipeline burst caches is to minimize wait states so that memory can be accessed as fast as possible by the microprocessor. Pipeline burst caches use two techniques: a burst mode that pre-fetches memory contents before they are requested, and pipelining so that one memory value can be accessed in the cache at the same time that another memory value is accessed in DRAM.
plasma display
A plasma display is an emissive flat panel display where light is created by phosphors excited by a plasma discharge between two flat panels of glass. Plasma display works by sandwiching a neon/xenon gas mixture between two sealed glass plates with parallel electrodes deposited on their surfaces. The plates are sealed so that the electrodes form right angles, creating pixels. When a voltage pulse passes between two electrodes, the gas breaks down and produces weakly ionized plasma, which emits UV radiation. The UV radiation activates color phosphors and visible light is emitted from each pixel.
platter
Platter, also known as hard disk platter, is a component of a hard disk drive, which may have one or more hard disk platters. Most platters require two read/write heads, one for each side. Typically made from metal or plastic, a hard disk platter is a rigid, circular disk. A thin layer of either iron oxide or another material that possesses magnetic properties coats each side of a hard disk platter.
PLCC: Plastic Leaded Chip Carrier
Plastic Leaded Chip Carrier (PLCC) is a square surface-mount chip package for low thermal output microprocessors that substitutes epoxy plastic for the ceramic materials that are commonly used to encase chips in systems designed for microprocessors that produce high thermal outputs that can melt the plastic epoxy. PLCCs are JEDEC standard compliant. The PLCC “J” Lead configuration requires less board space versus equivalent gull-leaded components.
PLD: Programmable Logic Device
A programmable logic device or PLD is an electronic component used to build digital circuits. Unlike a logic gate, which has a fixed function, a PLD has an undefined function at the time of manufacture. Before the PLD can be used in a circuit it must be programmed. A PLD consists of arrays of AND and OR gates. A system designer implements a logic design with a device programmer that blows fuses on the PLD to control gate operation.
PLED: Polymer (polymeric) Light-Emitting Diode
Polymer (polymeric) Light-Emitting Diode (PLED) is a polymer that emits light when subjected to an electric current. It is used as a thin film for full-spectrum color displays and requires a relatively small amount of power for the light produced. Polymers are substances formed by a chemical reaction in which two or more molecules are combined to form larger molecules. PLEDs are thin film displays that are created by sandwiching an undoped conjugated polymer between two proper electrodes at a short distance. The polymer emits light when exposed to electricity. PLEDs enable full-spectrum color displays and are relatively inexpensive compared to other display technologies such as LCD or OLED and require little power to emit a substantial amount of light.
plug
Plug is a connector used to link together devices. The male connector is the plug, the female the socket. This may pose a problem if both connectors have some male and female characteristics. The connector normally mounted on a cable is the plug, and the connector mounted on the equipment is the socket.
PMOS
P-channel metal-oxide semiconductor (PMOS) is a type of MOS IC using p-type semiconductor material for the channels.
PnP: Plug and Play
Plug and Play is a term used in the computer field to describe a computer's ability to have new devices, normally peripherals, added to it without having to reconfigure or (ideally) restart the computer. There are a number of terms or variations that describe similar abilities, including PnP, and hot swapping. Since the introduction of the NuBus, the Apple Macintosh has been a plug-and-play computer.
pointing device
A pointing device is a device with which you can control the movement of the pointer to select items on a display screen. Examples of pointing devices include mice, trackballs, joysticks, touchpads, and light pens. Movements of the pointing device are echoed on the screen by movements of the mouse pointer and other visual changes.
polyfont recognition
Polyfont recognition, usually used in conjunction with OCR software, refers to the capability of computer software, to read and recognize more than one types of font on a document.
port
Port means a few things in networking: (1) A hardware connection point for a cable at a network device. Hubs and switches typically provide multiple ports for connecting Ethernet devices. These hardware ports have different physical shapes such as male, female, round, rectangular, square, oblong, etc. (2) A network port is an identification of an application in the TCP- or UDP-transported datagram.
Port Mapped I/O
Port Mapped I/I (or Port I/O) is a method of performing input/output between the CPU and I/O devices in a computer. Port-mapped I/O uses a special class of CPU instructions specifically for performing I/O. This is generally found on Intel microprocessors, specifically the IN and OUT instructions which can read and write a single byte to an I/O device. I/O devices have a separate address space from general memory, either accomplished by an extra "I/O" pin on the CPU's physical interface, or an entire bus dedicated to I/O.
Port Switcing Hub
Port Switching Hub, also known as Switching hub, can forward packets to the specific port based on the packet's address, instead of simply rebroadcast every packet to every port as the conventional hub. Most switching hubs also support load balancing, so that ports are dynamically reassigned to different LAN segments based on traffic patterns.
posted write-through
Posted write-through is a cache with a posted write-through policy (e.g. Intel 80386) delays the write-back to main memory until the bus is not in use.
PowerPC
PowerPC is a family of RISC-based computer processors (chips) developed jointly by IBM, Apple Computer, and Motorola Corporation and used in IBM RS/6000 systems and Apple Macintosh computers. These chips are have the speed of the Pentium but use less power. PowerPC architecture is based on the POWER CPU chip, used in IBM RS/6000 workstations. The 601 is a 32-bit microprocessor with a 64-bit bus.
PPGA: Plastic Pin Grid Array
Plastic Pin Grid Array (PPGAs), developed by Intel to combat power supply decoupling issues in high-performance microprocessors, is a configuration for the microprocessor socket on a computer motherboard. This square chip packaging technology was designed for microprocessors with greater numbers of transistors on each chip than previous models. Unlike ceramic pin grid arrays (CPGA) or tape carrier packages (TCP), PPGA packages offer a greater amount of thermal resistance and improved electrical performance and power distribution, which directly affect the potential performance of microprocessors sensitive to heat transmission.
PPI: Pixels per inch
Pixels Per Inch (PPI), or pixel density, is a measurement of resolution of a monitor displaying an image or a printer printing a picture. This measurement is often referred to as dots per inch, though that measurement more accurately refers to the resolution of a computer printer. PPI may also be used to describe the resolution of an image scanner or digital camera; in this context, it is synonymous with samples per inch.
PRAM: Parameter RAM
Parameter RAM (PRAM), on Macintosh computers, is a small portion of RAM used to store information about the way the system is configured. For example, parameter RAM holds the date and time, desktop pattern, mouse settings, volume settings, and other control data set with control panels. It is battery-backed memory, equivalent to the "CMOS RAM" in IBM PC's, so it does not lose its contents when the power is turned off.
Primary cache
Primary cache, also known as Level 1 (L1) cache, is a memory cache built into the CPU. Primary cache is used by the central processing unit of a computer to reduce the average time to access memory. The cache is a smaller, faster memory which stores copies of the data from the most frequently used main memory locations. As long as most memory accesses are to cached memory locations, the average latency of memory accesses will be closer to the cache latency than to the latency of main memory.
primary storage
Primary storage, also known as main memory, refers to RAM (Radom Access Memory) of CPU. Computers use RAM to hold the program code and data during execution. One defining characteristic of RAM is that its accesses to different memory locations are almost always completed at about the same speed, in contrast to some other technologies that require a certain delay time for a bit or byte to “come around”.
print server
A print server is a networked computer or device to which one or more printers are connected and which accepts print jobs from other computers in the network. The print server then sends the data to the appropriate printer that it manages.
printer
In computing, printer is a computer peripheral device that produces a hard copy (permanent human-readable text and/or graphics, usually on paper) from data stored in a computer connected to it. There are many types of printers.
printer driver
Printer driver is a piece of software that converts the data to be printed to the form specific to a printer. The purpose of printer drivers is to allow applications to do printing without being aware of the technical details of each printer model. Whenever you print a document, the printer driver takes over, feeding data to the printer with the correct control commands. Most modern operating systems come with printer drivers for the most common types of printers, but you must install them before you can use the printer. You can also download updated drivers from the printer manufacturer's Web site.
printer engine
Printer engine is the main component of a printer that actually performs the printing. The printer engine determines how fast and at what resolution the printer can print. Many printers from various manufacturers use the same printer engines.
printer spooling
In print spooling, documents are loaded into a buffer (usually an area on a disk), and then the printer pulls them off the buffer at its own rate. Because the documents are in a buffer where they can be accessed by the printer, the user is free to perform other operations on the computer while the printing takes place in the background. Spooling also lets users place a number of print jobs on a queue instead of waiting for each one to finish before specifying the next one.
processor
A processor, also known as central processing unit (CPU), refers to the part of a computer that interprets and carries out, or processes, instructions and data contained in the software. Microprocessors are CPUs that are manufactured on integrated circuits, often as a single-chip package. Since the mid-1970s, these single-chip microprocessors have become the most common and prominent implementations of CPUs, and today the term is almost always applied to this form.
PROM: Programmable read-only memory
Programmable read-only memory (PROM) is a memory chip on which data can be written only once. Unlike RAM, PROMs retain their contents when the computer is turned off.
protocol stack
A protocol stack is a particular software implementation of a computer networking protocol suite. The terms are often used interchangeably. Strictly speaking, the suite is the definition of the protocols and the stack is the software implementation of them. For example, the TCP/IP protocol stack defined communication over the Internet.
proxy cache
Proxy cache is a facility in a proxy server that caches incoming Web pages on the hard disk. If the next page requested by a browser is already in the proxy cache, the page is retrieved locally instead of from the Internet. With proxy caches, the browsers must be configured to use the proxy server.
proxy gateway
Proxy gateway is a system which passes on a request for a URL from a World-Wide Web browser such as Mosaic to an outside server and return the results. This provides clients that are sealed off from the Internet a trusted agent that can access the Internet on their behalf. Once the client is properly configured, its user should not be aware of the proxy gateway. A proxy gateway often runs on a firewall machine. Its main purpose is to act as a barrier to the threat of crackers. It may also be used to hide the IP addresses of the computers inside the firewall from the Internet if they do not use official registered network numbers.
Proxy Server
A proxy server, also called proxy, is a computer network service that allows clients to make indirect network connections to other network services. A client connects to the proxy server, then requests a connection, file, or other resource available on a different server. The proxy provides the resource either by connecting to the specified server or by serving it from a cache. In some cases, the proxy may alter the client's request or the server's response for various purposes.
PS/2 port
PS/2 port connects a mouse or keyboard to a PC. The PS/2 port supports a mini DIN plug containing just 6 pins. Most PCs have a PS/2 port so that the serial port can be used by another device, such as a modem. The PS/2 port is often called the mouse port.
punchdown block
Punchdown block is a device that connects one group of wires to another group of wires through a system of metal pegs that the wires are attached to, often used in telecommunications closets that support local-area networks. Punchdown blocks are the predecessors to patch panels and were commonly used to support low-bandwidth Ethernet and token-ring networks. Punchdown blocks typically are not capable of supporting Cat-5 cabling, which is the common cable used in modern Ethernet designs.
PWM: Pulse Width Modulation
Pulse Width Modulation (PWM) is a digital control technique wherein the processor adjusts the duty cycle of a sequence of fixed-width pulses. PWM is used more to control external analog signals or mechanical devices than to transmit data.