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.

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PABX: A PABX (private automatic branch exchange) is an automatic telephone switching system within a private enterprise. Originally, such systems - called private branch exchanges (PBXs) - required the use of a live operator. Since almost all private branch exchanges today are automatic, the abbreviation "PBX" usually implies a "PABX."
Some manufacturers of PABX (PBX) systems distinguish their products from others by creating new kinds of private branch exchanges. Rolm offers a Computerized Branch Exchange (CABX) and Usha Informatics offers an Electronic Private Automatic Branch Exchange (EPABX).

PACKET: A packet is the unit of data that is routed between an origin and a destination on the Internet or any other packet-switched network. When any file (e-mail message, HTML file, GIF file, URL request, and so forth) is sent from one place to another on the Internet, the Transmission Control Protocol (TCP) layer of TCP/IP divides the file into "chunks" of an efficient size for routing. Each of these packets is separately numbered and includes the Internet address of the destination. The individual packets for a given file may travel different routes through the Internet. When they have all arrived, they are reassembled into the original file (by the TCP layer at the receiving end).

PACKET SWITCHING: A packet-switching scheme is an efficient way to handle transmissions on a connectionless network such as the Internet. An alternative scheme, circuit-switching, is used for networks allocated for voice connections. In circuit-switching, lines in the network are shared among many users as with packet-switching, but each connection requires the dedication of a particular path for the duration of the connection.

PAGE: 1) On the World Wide Web, a page is a file notated with the Hypertext Markup Language (HTML). Usually, it contains text and specifications about where image or other multimedia files are to be placed when the page is displayed. You can think of a Web site as a book (albeit a hypertext kind of book rather than a sequentially arranged kind of book) that arrives a page at a time as you request each one. Each page is an individual HTML file with its own Web address (URL). The first page you usually request at a site is known as the home page. (Most home pages have a default name that does not have to be specified; you only need to enter the domain name for the site itself.) With frames, multiple pages (HTML files) can be downloaded to a browser and presented on designated sections of the display screen at the same time.
2) In a computers random access memory (RAM), a page is a group of memory cells that are accessed as part of a single operation. That is, all the bits in the group of cells are changed at the same time. In some kinds of RAM, a page is all the memory cells in the same row of cells. In other kinds of RAM, a page may represent some other group of cells than all those in a row.
3) In computer systems that use virtual memory (also known as virtual storage), a page is a unit of data storage that is brought into real storage (on a personal computer, RAM) from auxiliary storage (on a personal computer, usually the hard disk) when a requested item of data is not already in real storage (RAM).
4) In printing, a page is what is printed on a single piece of paper.

PAP: 1) PAP (Packet-Level Procedure) is a full-duplex protocol for transferring packets between parties in an X.25 network. PAP supports data sequencing, flow control, accountability, and error detection and recovery.
2) PAP (Password Authentication Procedure) is a procedure used by PPP servers to validate a connection request. PAP works as follows:
After the link is established, the requestor sends a password and an id to the server.
The server either validates the request and sends back an acknowledgement, terminates the connection, or offers the requestor another chance.
Passwords are sent without security and the originator can make repeated attempts to gain access. For these reasons, a server that supports CHAP will offer to use that protocol before using PAP. PAP protocol details can be found in RFC 1334.

PASSWORD: A password is an unspaced sequence of characters used to determine that a computer user requesting access to a computer system is really that particular user. Typically, users of a multiuser or securely protected single-user system claim a unique name (often called a user ID) that can be generally known. In order to verify that someone entering that user ID really is that person, a second identification, the password, known only to that person and to the system itself, is entered by the user. A password is typically somewhere between five and 8 characters, depending on how the computer system is set up. When a password is entered, the computer system is careful not to display the characters on the display screen, in case others might see it.
Good criteria when choosing a password or setting up password guidelines include the following:
Not a password that someone can easily guess if they know who you are (for example, not your Social Security number, birthday, or maiden name)
Not a word that can be found in the dictionary (since there are programs that can rapidly try every word in the dictionary!)
Not a word that is currently newsworthy
Not a password that is similar to your previous password
A mixture of letters and at least one number
A word that you can easily remember
Many networks require that you change your password on some periodic basis.

PERL: Perl is a script programming language that is similar in syntax to the C language and that includes a number of popular UNIX facilities such as sed, awk, and tr. Perl is an interpreted language that can be compiled just before execution into either C code or cross-platform byte-code. When compiled, a Perl program is almost (but not quite) as fast as a fully precompiled C language program. Perl is regarded as a good choice for developing Common Gateway Interface (CGI) programs because it has good text manipulation facilities (although it also handles binary files). It was invented by Larry Wall.
In general, Perl is easier to learn and faster to code in than the more structured C and C++ languages. Perl programs can, however, be quite sophisticated. Perl tends to have devoted adherents.
Plug-ins can be installed for some servers (Apache, for example) so that Perl is loaded permanently in memory, thus reducing compile time and resulting in faster execution of CGI Perl scripts.

PHP: (Originally personal home page)
In Web programming, PHP is a script language and interpreter, similar to JavaScript and Microsoft's VBScript, that is freely available and used primarily on Linux Web servers. PHP (the initials come from the earliest version of the program, which was called "Personal Home Page Tools") is a cross-platform alternative to Microsoft's Active Server Page (ASP) technology (which runs only on Microsoft's Windows NT servers). As with ASP, the PHP script is embedded within a Web page along with its HTML. Before the page is sent to a user that has requested it, the Web server calls PHP to interpret and perform the operations called for in the PHP script. An HTML page that includes a PHP script is typically given a file name suffix of ".php" ".php3," or ".phtml". Like ASP, PHP can be thought of as "dynamic HTML pages," since content will vary based on the results of interpreting the script.

PHTML: A PHTML (or its sometimes called a PHP) page is a Web page that includes a script written in PHP, a language comparable to JavaScript or Microsofts VBScript. Like Microsofts Active Server Page (ASP) page, a PHTML page contains programming that is executed at the Web server rather than at the Web client (which is usually your Web browser). You may sometimes see a Web site whose address or URL ends with a file with a suffix of ".phtml"" or ".php3". Either of these suffixes indicate an HTML page that includes a PHP script.

PING: Ping is a basic Internet program that lets you verify that a particular Internet address exists and can accept requests. The verb ping means the act of using the ping utility or command. Ping is used diagnostically to ensure that a host computer you are trying to reach is actually operating. If, for example, a user can

PKZIP OR PKUNUZIP: Utilities for easily compressing and uncompressing DOS and Windows files. They use the .zip filename extension.

PLUG-IN: Plug-in applications are programs that can easily be installed and used as part of your Web browser. Initially, the Netscape browser allowed you to download, install, and define supplementary programs that played sound or motion video or performed other functions. These were called helper applications. However, these applications run as a separate application and require that a second window be opened. A plug-in application is recognized automatically by the browser and its function is integrated into the main HTML file that is being presented.
Among popular plug-ins to download are Adobes Acrobat, a document presentation and navigation program that lets you view documents just as they look in the print medium, RealNetworks streaming media player, and Macromedias Shockwave for DIrector, an interactive animation and sound player. There are now hundreds of possible plug-ins. Most users wait until they need a particular plug-in before they download it.

POP: Point of Presence, also Post Office Protocol -- Two commonly used meanings: Point of Presence and Post Office Protocol. A Point of Presence usually means a city or location where a network can be connected to, often with dial up phone lines. So if an Internet company says they will soon have a POP in Belgrade, it means that they will soon have a local phone number in Belgrade and/or a place where leased lines can connect to their network. A second meaning.
Post Office Protocol refers to the way e-mail software such as Eudora gets mail from a mail server. When you obtain a SLIP, PPP, or shell account you almost always get a POP account with it, and it is this POP account that you tell your e-mail software to use to get your mail.

POP3: POP3 (Post Office Protocol 3) is the most recent version of a standard protocol for receiving e-mail. POP3 is a client/server protocol in which e-mail is received and held for you by your Internet server. Periodically, you (or your client e-mail receiver) check your mail-box on the server and download any mail. POP3 is built into the Netmanage suite of Internet products and one of the most popular e-mail products, Eudora. It's also built into the Netscape and Microsoft Internet Explorer browsers.
An alternative protocol is IMAP (Interactive Mail Access Protocol). With IMAP, you view your e-mail at the server as though it was on your client computer. An e-mail message deleted locally is still on the server. E-mail can be kept on and searched at the server.
POP can be thought of as a "store-and-forward" service. IMAP can be thought of as a remote file server.
POP and IMAP deal with the receiving of e-mail and are not to be confused with the Simple Mail Transfer Protocol (SMTP), a protocol for transferring e-mail across the Internet. You send e-mail with SMTP and a mail handler receives it on your recipient's behalf. Then the mail is read using POP or IMAP.

PORT: 1) On computer and telecommunication devices, a port (noun) is generally a specific place for being physically connected to some other device, usually with a socket and plug of some kind. Typically, a personal computer is provided with one or more serial ports and usually one parallel port. The serial port supports sequential, one bit-at-a-time transmission to peripheral devices such as scanners and the parallel port supports multiple-bit-at-a-time transmission to devices such as printers.
2) In programming, a port (noun) is a "logical connection place" and specifically, using the Internets protocol, TCP/IP, the way a client program specifies a particular server program on a computer in a network. Higher-level applications that use TCP/IP such as the Web protocol, HTTP, have ports with preassigned numbers. These are known as "well-known ports" that have been assigned by the Internet Assigned Numbers Authority (IANA). Other application processes are given port numbers dynamically for each connection. When a service (server program) initially is started, it is said to bind to its designated port number. As any client program wants to use that server, it also must request to bind to the designated port number.
3) In programming, to port (verb) is to move an application program from an operating system environment in which it was developed to another operating system environment so it can be run there. Porting implies some work, but not nearly as much as redeveloping the program in the new environment. Open standard programming interfaces (such as those specified in X/Opens UNIX 95 C language specification and Sun Microsystems Java programming language) minimize or eliminate the work required to port a program.

PORTAL: 1) Portal is a new term, generally synonymous with gateway, for a World Wide Web site that is or proposes to be a major starting site for users when they get connected to the Web or that users tend to visit as an anchor site. There are general portals and specialized or niche portals. Some major general portals include Yahoo, Excite, Netscape, Lycos, CNET, Microsoft Network, and America Onlines AOL.com. Examples of niche portals include Garden.com (for gardeners), Fool.com (for investors), and SearchNT.com (for Windows NT administrators).
A number of large access providers offer portals to the Web for their own users. Most portals have adopted the Yahoo style of content categories with a text-intensive, faster loading page that visitors will find easy to use and to return to. Companies with portal sites have attracted much stock market investor interest because portals are viewed as able to command large audiences and numbers of advertising viewers.
Typical services offered by portal sites include a directory of Web sites, a facility to search for other sites, news, weather information, e-mail, stock quotes, phone and map information, and sometimes a community forum. Excite is among the first portals to offer users the ability to create a site that is personalized for individual interests.
The term portal space is used to mean the total number of major sites competing to be one of the portals.
2) In fantasy games, science-fiction, and some "New Age" philosophies, a portal is a gateway to another world of the past, present, or future, or to an expanded awareness.
3) In 3-D graphics development, portal rendering is a technique that increases the effect of realism and speeds up presentation.

POSTING: A single message entered into a network communications system.
E.g. A single message posted to a newsgroup or message board.

POTS: POTS is a term sometimes used in discussion of new telephone technologies in which the question of whether and how existing voice transmission for ordinary phone communication can be accommodated. For example, ADSL and ISDN provide some part of their channels for "plain old telephone service" while providing most of their bandwidth for digital data transmission.

PPP: PPP (Point-to-Point Protocol) is a protocol for communication between two computers using a serial interface, typically a personal computer connected by phone line to a server. For example, your Internet server provider may provide you with a PPP connection so that the providers server can respond to your requests, pass them on to the Internet, and forward your requested Internet responses back to you. PPP uses the Internet protocol (IP) (and is designed to handle others). It is sometimes considered a member of the TCP/IP suite of protocols. Relative to the Open Systems Interconnection (OSI) reference model, PPP provides layer 2 (data-link layer) service. Essentially, it packages your computers TCP/IP packets and forwards them to the server where they can actually be put on the Internet.
PPP is a full-duplex protocol that can be used on various physical media, including twisted pair or fiber optic lines or satellite transmission. It uses a variation of High Speed Data Link Control (HDLC) for packet encapsulation.
PPP is usually preferred over the earlier de facto standard Serial Line Internet Protocol (SLIP) because it can handle synchronous as well as asynchronous communication. PPP can share a line with other users and it has error detection that SLIP lacks. Where a choice is possible, PPP is preferred.

PSTN: The PSTN (public switched telephone network) refers to the worlds collection of interconnected voice-oriented public telephone networks, both commercial and government-owned. Its also referred to as the Plain Old Telephone Service (POTS). Its the aggregation of circuit-switching telephone networks that has evolved from the days of Alexander Graham Bell ("Doctor Watson, come here!"). Today, it is almost entirely digital in technology except for the final link from the central (local) telephone office to the user.
In relation to the Internet, the PSTN actually furnishes much of the Internets long-distance infrastructure. Because Internet service providers ISPs pay the long-distance providers for access to their infrastructure and share the circuits among many users through packet-switching, Internet users avoid having to pay usage tolls to anyone other than their ISPs.

PUBLIC ACCESS PROVIDER: An organization that provides Internet access for individuals or other organizations, often for a fee.

PUBLIC DOMAIN: Programs that are open to copy because their authors intended to share them with everyone else are in the public domain. The UNIX community has developed a number of such programs over the years. Programs in the public domain can be used without restriction as components of other programs. When reusing such code, it is good to understand its history so that you can be sure it really is in the public domain.