Packet - One unit of information that has been formatted for transmission on a network. A packet includes user data as well as the control and addressing information needed to send the packet to the correct destination.

PAL - Acronym for Phase Alternating Line. A video format used by many European countries and other countries outside North America. The PAL standard is 25 fps, 625 lines per frame, and interlaced.

Parallel Device - A printer or other device that sends and receives data eight bits at a time over eight parallel wires. A serial device is a device that sends and receives data one bit at a time over a single wire.

Parallel Interface - The condition of a computer and a peripheral device exchanging information eight bits at the same time along eight parallel wires. A serial interface is the condition of a computer and a peripheral device exchanging information one bit at a time along a single wire.

Parallel Port - A hardware connection in which a group of data bits typically 8 bits is sent at one time. Printers and webcams, for example, use parallel ports.

Parameter - A parameter is an additional value that you must provide along with a command. For example, in the Hn command, the letter n stands for a parameter whose value can be either 0 or 1. You type the actual command as either H0 or H1. Most AT commands require at least one parameter, denoted in command descriptions by the letter n. When you enter an AT command, you must substitute a valid parameter value for n. A few commands require a second parameter, denoted by x.

Parent - A computer whose shared directory domain provides configuration information to another computer.

Parity - A way of checking data to make sure bits of data didn't get lost or garbled during transmission.

Partition - A subdivision of a hard disk's area that is defined and used as a separate volume.

Pascal - A programming language taught in high school and college computer-science courses because it stresses a systematic approach to problem solving.

Passive Star - A type of star topology that has a lower limit on the number of branches allowed and the total length of the cable.

Password - A secret word that gives you, but no one else, access to your data or to messages sent to you through an information service.

Paste - To put a copy of the contents of the Clipboard whatever was last cut or copied at the insertion point.

Pathname - The complete name of a document beginning with the name of the disk, also called the volume name, the name of the subdirectory it's in if it's in one, and the name of the document. The pathname begins with a slash, and the parts of the pathname are separated with slashes. It's called a pathname because it describes the route to the document. Volume name is the name of a disk or its main directory.

PCI - Peripheral Component Interconnect, an industry-standard expansion bus.

PCMCIA or PC Card - Short for Personal Computer Memory Card International Association, and pronounced as separate letters, PCMCIA is an organization consisting of some 500 companies that has developed a standard for small, credit card-sized devices, called PC Cards. 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. All three have the same rectangular size 85.6 by 54 millimeters, but different widths. Type I cards can be up to 3.3 mm thick, and are used primarily for adding additional ROM or RAM to a computer. Type II cards can be up to 5.5 mm thick. These cards are often used for modem and fax modem cards. Type III cards can be up to 10.5 mm thick, which is sufficiently large for portable disk drives.

PDF - Short for Portable Document Format, a file format developed by Adobe Systems. PDF captures formatting information from a variety of desktop publishing applications, making it possible to send formatted documents and have them appear on the recipient's monitor or printer as they were intended. To view a file in PDF format, you need Adobe Acrobat Reader, a free application distributed by Adobe Systems.

Percent Symbol %
- The command-line prompt in the Terminal application. The prompt indicates that you can enter a command.

Peripheral Device - A device that is connected to the computer, like a printer or a modem.

Perl (Practical Extraction and Reporting Language) - Perl is a scripting language commonly used with web servers.

PHP-Hypertext Preprocessor - A scripting language embedded in HTML that is used to create dynamic Web pages.

PICT - A Macintosh picture file format that does not apply compression to an image. It is therefore termed a lossless format. PICT file format maintains the same quality level from copy to copy. The PICT file format is recommended when exporting a still image from a DV clip if the intent is to reuse the image in a movie in iMovie.

PILOT - Acronym for Programmed Inquiry, Learning, Or Teaching. A programming language that lets teachers design their own educational software. SuperPILOT is the Apple version of the PILOT programming language.

Pinfeed Paper - A stack of attached, perforated sheets designed to feed into a printer without much human intervention.

Pixel - Contraction of the words picture and element. In graphics mode, text and graphics are formed by patterns of dots called pixels.

PL/1 - A complex, but flexible programming language said to combine the best features of Fortran, a programming language suited to scientific applications, and COBOL, a programming language suited to business applications.

Playback Controls - In iMovie, the controls under the monitor and on the music palette. These controls are Play, Pause, Fast Forward, Rewind/Review, and Stop.

Playlist - A set of media files in the QTSS or DSS media folder specified to play one after the other or in random sequence.

Plotter - A device that prints charts and graphs by means of pens whose movements are programmed.

Pointer - A marker that moves across the screen when you move the mouse across your desk in mouse-based applications. Also known as a cursor.

Point-to-Point Protocol PPP - A protocol for dialup modem access. PPP support includes TCP/IP as well as the PAP and CHAP authentication protocols.

POP Post Office Protocol - A protocol for retrieving incoming mail. After a user retrieves POP mail, it is stored on the user's computer and usually is deleted automatically from the mail server.

Port - A connector on the back panel of the Apple IIgs for connecting peripheral devices.

Portable Operating System Interface POSIX
- An operating-system interface standardization effort supported by ISO/IEC, IEEE, and The Open Group.

Portables - Apple hardware you can take easily from place to place, such as Apple's iBook and PowerBook. Windows PC manufacturers sometimes refer to portables as laptops or notebooks.

POST - power-on self test.

PostScript - A language that is used to describe graphic objects on a printed page. A PostScript interpreter is software that executes a PostScript language program and turns the description of an object into bits in a frame buffer. PostScript is a trademark of Adobe Systems Incorporated.

Power Light - A light that tells you whether or not the computer is on.

Power Strip - A device that plugs into one three-hole, grounded outlet, but that can accommodate four or six three-pronged plugs. A must if you have more than two devices that need to be plugged into a grounded, three-hole outlet.

Power Switch - A rocker switch on the back of the computer that you switch on when you want to use your computer.

PowerPC - Any one of the RISC-based processing chips 601, 603, 604, 604e, G3, or G4 designed by Apple, IBM, and Motorola.

PRAM - Parameter RAM. PRAM stores date and time settings and other system preference data.

Predefined Accounts - User accounts that are created automatically when you install Mac OS X. Some group accounts are also predefined.

- The act of interrupting a currently running task in order to give time to another task.

Preferences Cache - A storage place for computer preferences and preferences for groups associated with that computer. Cached preferences help you manage local user accounts on portable computers.

Prefix - The first part of a pathname the name of the disk and, if you like, the name of a subdirectory. Applications that ask you to type a pathname usually let you set a prefix so you don't have to type the complete pathname every time you want to work with a document on a particular disk or in a particular subdirectory. Once the prefix is set, all you do is type the rest of the pathname.

Pre-Roll - Rewinding the tape in a camcorder to a few seconds before the point at which the user intends to start capturing video.

Presets - Initial default attributes you specify for new accounts you create using Server Manager. You can use presets only during account creation.

Press - To position the pointer on something and then hold down the mouse button without moving the mouse. To hold down a key on the keyboard.

Primary Group ID - A unique number that identifies a primary group.

Primary Group - A user's default group. The file system uses the ID of the primary group when a user accesses a file he or she doesn't own.

Print Buffer Card - A card that plugs into a printer interface card that lets your Apple IIgs send an entire document to the printer at one time so you can use your computer for other things while the document is being printed.

Print Server - A combination of hardware and software that stores documents sent to it over a network and manages the printing of the documents on a printer. A print server completely frees a computer of a printing task so that the computer is free to be used for other work. Background printing-is a software application that runs on a computer as a background process, allowing the user to work on other tasks while a document is being printed.

Print Spooler - A program that stores documents to be printed, thereby freeing memory and allowing other functions to be performed while printing goes on in the background.

Printer Access Protocol PAP - Printer Access Protocol. Used for spooling print jobs and printing to network printers.

Printer - A device that produces a paper copy of the information you create using the computer.

Privileges - Settings that define the kind of access users have to shared items. You can assign four types of privileges to a share point, folder, or file-read and write, read only, write only, and none no access.

Processor - Also called a CPU-Central processing unit, a type of microprocessor. In current Power Mac, iMac, PowerBook, and iBook computers, the CPU is a PowerPC G3 or G4 chip. Earlier models contained PowerPC 601, 603, 604, 604e and Motorola 680x0 chips.

ProDOS - Stands for Professional Disk Operating System which is the primary operating system for the Apple IIgs. ProDOS 8 and ProDOS 16 refer to versions of ProDOS designed for 8- and 16-bit microprocessors respectively.

Program Disk - A disk that contains an operating system and a self-starting application program.

Program Selector - A program that lets you switch application programs without restarting the computer.

Programmer - A person who writes computer programs.

Program - To write instructions for the computer to talk to the computer in terms it understands. n. A set of instructions that tells the computer what to do.

Progressive Download
- Movie data that is pushed via HTTP to the client. The movie can be viewed by the user as it is being transferred. This is not a form of media streaming.

Progressive Video - A video frame format that progressively scans all lines in a frame. Interlaced video is a video frame format that divides the lines into two fields, each consisting of alternating odd and even lines, which are scanned at different times. Used in standard definition video.

Project Builder - A tool used to manage the development of a WebObjects application or framework.

Prompt - A character displayed on the screen to prompt the user to take some action. For example, a bracket prompt character is used in the Applesoft BASIC programming language.

Property - In Entity-Relationship modeling, an attribute or relationship. Attribute is an In Entity-Relationship modeling, an identifiable characteristic of an entity. For example, lastName can be an attribute of an Employee entity. An attribute typically corresponds to a column in a database table. A column-In a relational database, is the dimension of a table that holds values for a particular attribute. For example, a table that contains employee records might have a column titled LAST_NAME that contains the values for each employee's last name.

Protocol Architecture - The system of network protocols that determines how the network's components--such as devices, cable, and software--work together to provide network services to users.

Protocols - A formal set of rules for sending and receiving information on a network.

Proxy Server - A server that sits between a client application, such as a Web browser, and a real server. The proxy server intercepts all requests to the real server to see if it can fulfill the requests itself. If not, it forwards the request to the real server.

Public-Domain Software - Software that is free for the taking. You can get it at users-group meetings or through computer bulletin boards.

Pull List - A film list Cinema Tools users can export, in which cut list shots are listed in the order that they can be found on the negative rolls. The lab refers to a pull list when going through your negative rolls to pull shots for a workprint or original camera negative cut.

Pull-Down Menu - A menu that is hidden until you press on its title with the mouse.

Pulse Dialing - Pulse dialing is a method of dialing in which the modem sends a set of pulses for each number one pulse for the number 1, two pulses for 2, and so on.

Punchdown Block - A wiring distribution block that is usually located in a telephone wiring closet.