Barrons Publishing Dictionary of Computer and Internet Terms 10th

pin

1.a movable stiff wire that presses on the ribbon of a dot-matrix printer under computer control in order to make dots on the paper.

2.a stiff prong in an electronic connector. For example, a VGA video connector has 15 pins; a serial port connector has 9 or 25 pins.

PIN (Personal Identification Number) a number used as a password by a computer user.

ping the command, on a TCP/IP network, that sends a test data packet to another site and waits for a response.

ping flooding the practice of maliciously disrupting a computer by pinging it continuously (i.e., flooding it with test data packets to which it must respond). Also known as SMURFING. See DENIAL-OF-SERVICE ATTACK.

pipe

1. a way of stringing two programs together so that the output of one of them is fed to the other as input. For example, the Windows command

C:\> dir | sort | more

invokes dir (which lists the names of the files on a disk), feeds its output to sort (which puts the items in alphabetical order), and feeds that output to more (which displays it one screenful at a time).

See also BROKEN PIPE.

2. the character | (the pipe symbol).

pipeline a device within a CPU that enables it to fetch (read) instructions in advance of executing them, so that whenever an instruction is completed, the next instruction is ready to execute. This is a way of partly overcoming the Von Neumann bottleneck. See also

piracy the unauthorized copying of software, which is forbidden by law.

See COPYRIGHT; SOFTWARE LICENSE.

pitch (typesetting) the number of characters per inch in a particular size and style of type. Fixed-pitch type has every character the same width; pro- portional-pitch type has some characters wider than others (e.g., M wider than I), and the pitch can be measured only approximately as the average of many different letters. See Figure 104, page 193.

pivot table a multi-dimensional data table that can be rearranged to allow different views of the data. For example, suppose you need to keep track of a budget with two divisions and three spending categories for three months. Here is the original data:

Or, you might wish to consolidate all of the spending categories and create a view like this:

Excel contains a wizard that automatically creates pivot tables.

PIX (Private Internet Exchange) a type of secure hardware FIREWALL developed in 1994 by John Mayes and Brantley Coile at Cisco Systems. It will translate network addresses, so the internal network can use IP addresses of its own choosing without worrying about clashes with IP addresses in the worldwide Internet. It was one of the first implementations of NAT (network address translation).

pixel one of the individual dots that make up a graphical image. For example, an xGA color screen in high-resolution mode consists of a 1024 × 768 pixel array. A program can draw pictures on the screen by controlling the color of each pixel. See GRAPHICS.

pixelate, pixelize to transform a bitmap image into rectangular blocks of uniform color, as if the pixels were much larger than before.

FIGURE 198. Pixelated image

PKCS (Public-Key Cryptography Standards) a set of standards developed by RSA Laboratories and others. Information on the web is available at www.rsa.com/rsalabs/pubs/PKCS.

PL/1 (PL/I) a powerful programming language developed by IBM in the early 1960s to accompany its System/360 computer. The name stands for Programming Language One.

PL/1 can be described as a combination of ALGOL 60 block structure, FORTRAN arithmetic, and COBOL data structuring. PL/1 is the language of choice for writing complex programs on IBM mainframe computers, but it has received little use on other types of machines.

planar

1.(adjective) flat. For example, planar transistors are made of flat pieces of silicon.

2.(adjective) situated on the motherboard of a computer (e.g., planar RAM).

3.(noun) motherboard. See MOTHERBOARD; contrast DAUGHTERBOARD;

RISER.

plane

1.in geometry, all the points on a flat surface. Thus a plane is a twodimensional space on which things have length and width but no thickness.

2.in computer graphics, one of several images that are superimposed to produce the final image. For example, many video cards have separate planes (internal bitmaps) for red, green, and blue. The complete image is a combination of the images stored on the three planes. See CHANNEL.

plasma glowing ionized gas. See GAS PLASMA DISPLAY.

platform a piece of equipment or software used as a base on which to build something else. For example, a mainframe computer can serve as a platform for a large accounting system. Microsoft Windows serves as a platform for application software.

plenum-rated (describing cable) suitable for use in places where air circulates, such as above suspended ceilings. (A plenum is a place full of air, the opposite of a vacuum.) Plenum-rated cable is fire resistant and does not give off noxious fumes when overheated. Contrast RISER-RATED.

plotter a device that draws pictures on paper by moving pens according to directions from a computer. See GRAPHICS.

Plug and Play a standard way of configuring PC-compatible computer hardware automatically, developed by Microsoft and a number of other companies in the mid-1990s. Plug and Play hardware is compatible with conventional hardware (ISA, PCI, PCMCIA, USB, etc.) but has additional capabilities. Each card or accessory inserted into a computer contains identifying information that can be read by the BIOS and the operating system. Thus, the computer can see all the installed accessories and can configure itself to use them appropriately.

plug-in an accessory program that provides additional functions for a main application program. Plug-ins have to be loaded at the same time as the main program; they then show up as an option in an appropriate menu. Plug-ins are also added to a web browser to allow it to view additional file formats, such as multimedia shows.

PMS see PANTONE MATCHING SYSTEM.

PNP one of the two types of bipolar TRANSISTORs (contrast NPN).

PnP abbreviation for PLUG AND PLAY.

podcasting (from iPod and broadcast, but not confined to the Apple iPod) the practice of preparing audio and video programs like radio and TV broadcasts, but distributing them through the Internet for playback on MP3 players, iPods, and similar devices. See IPOD.

FIGURE 199. Point (in typography)

point

1.in geometry, an exact location; in graphics, a precise location or single PIXEL.

2.a unit of typographical measurement equal to 1⁄72 inch. The height of type is usually expressed in points. However, this is not a measurement of the size of the letters, but rather of the wooden blocks on which the metal type was mounted for printing presses. This usually included some space at the top of the tallest capital letters and below the descenders. Therefore, dif-

ferent typefaces of the same point size may actually differ in size. To this day, even digitized typefaces show some of the same idiosyncrasies. A desire to be faithful to the original designs has prevented the type’s apparent size from being regularized. See LEADING; TYPEFACE; TYPESETTING MISTAKES.

FIGURE 200. 24-point type samples

point-of-sale system a computer used in place of a cash register where merchandise is sold. Besides keeping track of cash, the computer can keep track of inventory and print informative invoices and receipts, and perhaps automatically deduct funds from the customer’s account.

point release a minor upgrade of a piece of software, such as the upgrade from version 2.0 to 2.1.

point-to-point protocol see PPP; PROTOCOL.

pointer

1.an arrow-like symbol that moves around a computer screen under the control of the user. For example, to execute a command in a windowed operating system, use the mouse to move the pointer to the icon representing that command, and then quickly press the mouse button twice.

2.a data item consisting of an address that tells where to find a desired item. For examples, see LINKED LIST; TREE. Pascal, C, and many other programming languages provide a specific data type called a pointer variable that can be used to keep track of data structures that vary in size as the program is executed.

3.a device for pointing to a board or projection screen using a stick or a laser beam.

pointing device a computer peripheral that allows you to control your computer in a graphical user interface (GUI). The most familiar pointing device is a MOUSE, but some people prefer a TRACKBALL or a GRAPHICS TABLET. The pointing device on a LAPTOP is often a TOUCHPAD or a button that works like a miniature joystick.

Polish notation a way of writing algebraic expressions that does not require parentheses to state which operations are done first. It is named in honor of its inventor, Jan Lukasiewicz (1878–1956), whose name most English-speaking mathematicians cannot pronounce. The ordinary algebraic expression

4 + (5 – 3) + 2

translates into Polish notation as

4 5 3 – + 2 +

To evaluate the expression, work through it from left to right until you encounter an operation (a plus or minus), then perform that operation on the numbers immediately to the left of the operator, replace the numbers and the operator with the result of the operation, and keep going in the same manner. Thus,

4 5 3 – + 2 +

simplifies to

4 2 + 2 +

6 2 +

8

This is technically known as reverse Polish notation (RPN); the expression can also be written in the other direction and worked through from right to left. Many calculators and programming language interpreters translate expressions into Polish notation in order to evaluate them. Also, Hewlett-Packard calculators use Polish notation rather than parentheses on the ground that Polish notation is easier to work with once the user becomes accustomed to it.

polygon a closed geometric figure with any number of straight sides. Triangles, squares, pentagons (five-sided), hexagons (six-sided), heptagons (seven-sided), and octagons (eight-sided) are all examples of polygons.

FIGURE 201. Polygons

polymorphism the use of different procedures, each with the same name, which are associated with different object types. For example, procedures named draw could be associated with the types point, circle, and square. Calling draw for any particular object then activates the right drawing procedure for that type. See OBJECT-ORIENTED PROGRAMMING.

Ponzi scheme see PYRAMID SCHEME.

pop to remove the topmost item from a stack. See STACK.

POP

1.Post Office Protocol, a standard protocol for delivering e-mail to personal computers. See PROTOCOL.

2.point of purchase (point of sale). For example, a POP computer is a computer used as a cash register. See POINT-OF-SALE SYSTEM.

3.point of presence, a place where an INTERNET SERVICE PROVIDER can be accessed, such as a local telephone number.

pop-under ad an advertisement that appears automatically underneath (behind) the WEB PAGE you are viewing. Although pop-under ads are less intrusive than pop-up ads, they are still unwelcome because of the clutter they generate. See BANNER AD; MOUSETRAP; POP-UP AD.

pop-up ad an advertisement that appears automatically in a separate window when you access a WEB PAGE. See ADWARE. Compare BANNER AD;

POP-UNDER AD.

pop-up menu see PULL-DOWN MENU.

pornography publications or images whose primary purpose is to stimulate sexual appetite. See also INDECENCY; OBSCENITY.

Even the most innocent Internet user occasionally stumbles upon pornography. Some pornographers send advertisements to all the e-mail addresses they can obtain or make up (see SPAM). (Such e-mail does not indicate that the recipient has been viewing pornographic web pages, even if it says that it does.) Others rig their web pages so that SEARCH ENGINEs will lead users to them who are looking for something else.

Many individuals find pornography strongly addictive. The purpose of pornography is to make money, and the only reason it is given away free is to get people “hooked” so that they will pay for more.

In the United States, most of the pornography on the Internet is legal, but sexually explicit images of children are not, and images of sexual behavior may not be legal, depending on local laws. (See COMPUTER LAW; OBSCENITY.) Law enforcement is hampered by the difficulty of determining the physical locations of web sites. Note however that because the laws prohibit distribution of obscene material, a link to an obscene site can itself be illegal.

There have been various efforts to keep pornography from reaching children and unwilling audiences. The Communications Decency Act of 1996 was struck down because it assumed, incorrectly, that Internet service providers can control the information sent through their computers; replacement legislation has been proposed. Schools and libraries sometimes use “filtering” software to block access to known pornographic web sites, but the filtering process is imperfect. See ICRA.

Pornography is associated with credit card fraud and other crimes. Several Internet pornography vendors have been caught making unauthorized charges to credit card numbers, presumably expecting the victims to be too embarrassed to complain. In some cases the numbers were stolen or made up and belonged to people who had never had any contact with the vendors.

It is naive to describe pornography as “victimless.” The most obvious victims are the individuals who become addicted, and whose relationships and even marriages are damaged. The young people hired to pose for pornographic pictures are also victims of exploitation.

port

1. to adapt a program from one kind of computer to another. For example, some PC programs have been ported to the Macintosh.

2.a connection where a computer can be connected to an external device, such as a modem, printer, or tape drive. See PARALLEL; SCSI; SERIAL; USB.

3.a unique number used by a microprocessor to identify an input-out- put device. For example, the hexadecimal number 3F8 is the port address for part of the circuitry that controls the first serial port (COM1) on PC-compatible computers.

4.a number identifying the type of connection requested by a remote computer on the Internet. See URL.

port replicator a DOCKING STATION for a portable computer that contains serial and parallel ports (and perhaps other ports, such as USB) which substitute for those in the computer itself.

portable

1.able to be carried around. A portable computer is larger than a laptop computer, but is still easily movable.

2.(said of programs) able to run on more than one type of computer.

Portable Document File see PDF.

portal a web site designed for people to visit when they are looking for links to other sites. Examples include www.msn.com and www.yahoo.com as well as the home pages of various Internet service providers.

portrait the position in which a sheet of paper is taller than it is wide, like a portrait painting. Most printers print with the paper in portrait orientation. If the printed image can be turned sideways, the result is called landscape orientation. See Figure 148, page 276.

POS

1.point of sale. See POINT-OF-SALE SYSTEM.

2.programmable option select, the system for recording the configuration of a computer into CMOS RAM so that the computer can boot successfully. See CMOS RAM.

POSIX (usually understood as “portable operating system interface based on UNIX” though this is not its official definition) an IEEE standard set of operating system functions available to software. The POSIX standard makes it possible to write programs that will run under any POSIXcompliant operating system by simply recompiling them. Windows 95, 98, and Me are partially POSIX-compliant; Windows NT, 2000, XP, and Vista are more so. POSIX is a trademark of the IEEE. See IEEE; Z/OS.

post to place a message in a NEWSGROUP, BBS, WEB PAGE, or other public discussion forum.

posting a message placed in a NEWSGROUP, BBS, or other public discussion forum.

PostScript a programming language for controlling laser printers and other graphical output devices, developed by Adobe Systems of Palo Alto, California. A PostScript printer accepts not only characters to be printed