Glossary

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 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 a PDF reader, such as Adobe Reader

 POP3 Server

A POP server uses the Post Office Protocol, to hold users' incoming e-mail until they read or download it.

 PPP

An acronym for Point-to-Point Protocol, PPP is a communications protocol used to transmit network data over telephone lines. It allows you to connect your computer to the Internet itself, rather than logging on through an Internet service provider's host computer. This type of connection lets you communicate directly with other computers on the network using TCP/IP connections. It is part of the TCP/IP suite of programs necessary to connect to and use the Internet.

 Password

A password is a code or word used to gain access to restricted data on a computer network. While passwords provide security against unauthorized users, the security system can only confirm that the password is legitimate, not whether the user is authorized to use the password. That's why it is important to safeguard passwords: Never disclose your password. Devise a password that consists of letters, numbers, and symbols.

 Perl

An acronym for Practical Extraction and Reporting Language, PERL is a robust programming language frequently used for creating CGI programs on web servers. PERL is faster than UNIX shell script programs, it can read and write binary files, and it can process very large files. The major advantage of PERL over C as a programming language is that PERL does not need to be compiled.

 Ping

Ping tests the Internet to see what systems are working. Ping can also test and record the response time of accessing other companies. This provides a systems administrator with valuable information on what networks are overloaded so access times can be optimized.

 Pixel

A pixel, short for picture element, is the smallest element that can be displayed on a video screen or computer monitor, and is often used as a unit of measurement for image size and resolution. The number of pixels (width and height) in an image defines its size, and the number of pixels in an inch defines the resolution of the image.

 Plug-in

A plug-in extends the capabilities of a web browser, such as Netscape Navigator or Microsoft Internet Explorer, allowing the browser to run multimedia files. The term "plug-in" is used in two ways on the Internet. The technical definition of a plug-in is a small add-on piece of software that conforms to Netscape Navigator standard. Other browsers however, including Internet Explorer, support many Netscape plug-ins. But Explorer actually uses a different software standard, called an ActiveX control, instead of plug-ins.

 Port

Port can mean two things: To transfer or translate data or program files from one computer platform to another, such as from a PC to a Macintosh. Software programs usually have to be rewritten to be successfully ported. A connector on a computer to which peripheral devices, such as a printer or modem, are attached. Typically, these are serial ports, parallel ports, and modem ports.

 Posting

A posting is an e-mail message posted to an electronic communication service, such as a newsgroup

 Protocol

A protocol is the standard or set of rules that two computers use to communicate with each other. Also known as a communications protocol or network protocol, this is a set of standards that assures that different network products or programs can work together. Any product that uses a given protocol should work with any other product using the same protocol.

 Proxy Server

A server that sits between a client application, such as a Web browser, and a real server. It 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. Proxy servers have two main purposes:
- Improve Performance: Proxy servers can dramatically improve performance for groups of users. This is because it saves the results of all requests for a certain amount of time. Consider the case where both user X and user Y access the World Wide Web through a proxy server. First user X requests a certain Web page, which we'll call Page 1. Sometime later, user Y requests the same page. Instead of forwarding the request to the Web server where Page 1 resides, which can be a time-consuming operation, the proxy server simply returns the Page 1 that it already fetched for user X. Since the proxy server is often on the same network as the user, this is a much faster operation. Real proxy servers support hundreds or thousands of users. The major online services such as Compuserve and America Online, for example, employ an array of proxy servers.
- Filter Requests: Proxy servers can also be used to filter requests. For example, a company might use a proxy server to prevent its employees from accessing a specific set of Web sites.