PAL: Phase Alternating Line. A European video standard that has a broadcast resolution of 625 lines (at 25 interlaced frames per second) and is similar yet different from the NTSC standard used in the United States and Japan. VHS tapes and DVDs recorded for PAL are not playable on equipment set up for NTSC and vice-versa.

PALETTE: A grouping of graphic tools (e.g. Select, Paint Brush, Magic Wand, etc.) that is found in graphics and photo-enhancement software and is usually indicated by a row of tool icons or toolbox. Mouse-clicking any one of the icons activates the tool and often brings up a dialog box containing specific options.

PARALLEL INTERFACE: A type of input/output port that is found on Windows-based computers and is typically used for connecting printers, modems, and other peripheral devices. Data is simultaneously sent and received, at several bits at a time, over individual but adjacent wires.

PARC: Palo Alto Research Center. Xerox Corporations research and development center where the first graphical user computer interface was developed.

PARITY: The programming technique of adding an extra bit to a block of bits in data transmission that is used to verify accuracy. The extra bit is called a parity bit.

PARTITION: A method of dividing parts of a computers hard disk into individual sections which the computer treats as separate hard disks with individual names. (My partitions are named after Snoopys brothers and sisters; OK, Im sick.) Each section is called a partition and the act of creating these sections is called partitioning.

PATCH: A small program that is used to modify an application to repair bugs or conflicts with other software.

PC: The generic term for Personal Computer. Although originally trademarked by IBM to describe its first generation personal computer, its often used (incorrectly, I think) to describe all Microsoft Windows-based computers.

PCD: This is an extension used in the Windows environment to describe Kodaks Photo CD graphics file format. (See Photo CD.)

PCL: Printer Control Language was first used by Hewlett-Packard LaserJet printers, but has become a standard that is used by many printers and imagesetters.

PCM: Pulse Code Modulation.

PCMCIA: Personal Computer Memory Card International Association now officially called PC Card, but used less and less as memory cards get tinier and tinier.

PCX: Not an acronym and doesnt stand for anything specific. This is a bitmapped file format originally developed for the popular program PC Paintbrush.

PDA: Personal Data Assistant, such as the popular Palm Pilot or Handspring Visor.

PDF: Portable Document Format. A cross-platform file format produced by Adobe Systems Acrobat software that preserves the fidelity of all types of content including text and graphics. The file format is compatible across a wide variety of computer platforms, printers and electronic distribution methods. A free Acrobat Reader software (www.adobe.com) lets users view, navigate and print PDF files, and supports both Mac OS and Microsoft Windows environments.

PERIPHERAL: Any external input or output device that is connected to a computer. While peripheral, strictly speaking, refers to devices that are not built into the computers case, CD-ROM and DVD drives have become so common that such drives might be called a peripheral, even though they are actually physically part
of the computer.

PET: Personal Electronic Transaction. Introduced in 1977, the Pet computer was one of the first personal computers. It was a CP/M and floppy disk-based personal computer built by Commodore, who went on to create the innovative but ill fated Amiga.

PHOSPHOR: A rare earth material used as a coating inside the back of a Cathode Ray Tube. When struck by an electron beam, a phosphor emits light for a few milliseconds. In color monitors, red, green and blue, phosphors are grouped into clusters called triads.

PHOTO CD: A proprietary process of Eastman Kodak that places digitized photographic files onto a CD-ROM disc. Now seemingly abandoned by Kodak in favor of its JPEG-based Picture CD product that offers lower cost but unfortunately lower quality.

PIEZOELECTRIC: The property of some crystals that oscillate when subjected to electrical voltage. Epson uses this form of technology in their Stylus series of ink jet printers. On the other hand, piezo-electric (with hyphen) technology generates electricity when mechanical stress is applied.

PIXEL: Pixel is an acronym for picture element. A computers screen is made up of thousands of colored dots of light that, when combined, can produce a photographic image. A digital photographs resolution, or visual quality, is measured by the width and height of the image as measured in pixels.

PLUG-IN: Plug-ins are small software applications that increase the functionality and customize off-the-shelf graphic programs, such as Adobe Photoshop. You can think of plug-ins as additional blades or tools for your Swiss Army knife, and selecting the right one can make a tough graphics job easier and a difficult job practical. Plug-ins are easy to use and easier to install: they are simply copied into the Plug-in folder of a program, and after that, they appear as menu items in that program. They are, in effect, plugged in to the software and after installation become an integral part of it. The de facto plug-in standard was created by Adobe for their Photoshop image-manipulation program, but Photoshop compatible plug-ins can be used with many other programs, including Uleads PhotoImpact, Corels Painter and Dabbler, Corel PhotoPaint, JASCs PaintShop Pro, and MicroFrontiers Color-It!, Enhance, and Digital Darkroom. Other graphic programs, such as Adobe PageMaker, Denebas Canvas, and Macromedias Director, and Freehand accept compatible plug-ins as well.

PMMU: Paged Memory Management Unit.

PMT: Photomultiplier Tubes, a type of sensing technology used in drum scanners.

PORT: Some expansion cards have connectors that stick out the back of the computers. These connectors are called ports and allow different kinds of external devices, such as printers, to be connected. Sometimes these ports are built into the computers motherboard.

PORTRAIT MODE: The orientation of a graphic or photographic image in which its shorter dimension is the horizontal side. Photographers call this kind of photograph a vertical image. The opposite is horizontal or landscape mode.

POSTSCRIPT: A programming language originally created by Adobe Systems that defines shapes as Bezier (Bez-e-ay) curves and interprets them using mathematical formulae. PostScript compatible output devices uses these definitions to reproduce the image on your computer screen or as output.

PPA: Professional Photographers of America. Professional Photographer, the official journal of the PPA, was founded in 1907 by Charles Abel and is the oldest exclusively photographic publication in the Western hemisphere.

PPD FILE: PostScript Printer Description. Since PostScript is device-independent, a PPD file uses its information about a specific printer to take advantage of its built-in features.

PRAM: Parameter Random Access Memory. The place on the Power Macintoshs motherboard where the computers system defaults are stored. PRAM is battery-powered to keep that information hot. TIP: If your Mac is acting strangely, zapping the PRAM is one of the first things you can try to fix it. If the PRAM is corrupted by who knows what, zapping itsetting everything to zerowill often solve the problem. Look in your manual for instructions how to do this.

PRINTER: A peripheral device connected to a computer that produces paper-based (hard copy) output from data stored and perhaps manipulated by the computer user.

PROGRAM: A series of instructions, written by programmers that are used by computers to process data or images. Often called software or software program, although that latter term seems redundant to me.

PROTOCOL: The communications standards that apply to computers and other devices connected to a network or between computers and the World Wide Web.

PSD: This is an extension used in the Windows environment to describe Adobes proprietary Photoshop file format.