American Standard Code for Information Interchange. Pronounced ask-ee, ASCII is a code for representing English characters as numbers, with each letter assigned a number from 0 to 127. For example, the ASCII code for uppercase M is 77. Most computers use ASCII codes to represent text, making possible the transfer of data from one computer to another. The standard ASCII character set uses seven bits for each character, with several larger character sets that use 8 bits, adding 128 additional characters. The extra characters are used to represent non-English characters, graphics symbols and mathematical symbols.
Pronounced bawd, the number of signaling elements that occur each second. The term is named after J.M.E. Baudot, the inventor of the Baudot telegraph code. At slow speeds, only one bit of information is encoded in each electrical change, so the baud indicates the number of bits per second that are transmitted. For example, 300 baud means that 300 bits are transmitted each second (abbreviated 300 bps ).

Binary digits

Short for binary digit, the smallest unit of information on a machine. The term was first used in 1946 by John Tukey, a leading statistician.
  • A single bit holds only one of two values: 0 or 1. More meaningful information is obtained by combining consecutive bits into larger units. For example, a byte is composed of eight consecutive bits.
  • Computers are sometimes classified by the number of bits they can process at one time or by the number of bits they use to represent addresses. These two values are not always the same and can lead to confusion. Classifying a computer as a 32-bit machine might mean that its data registers are 32 bits wide or that it uses 32 bits to identify each address in memory. Larger registers make a computer faster, while using more bits for addresses enables a machine to support larger programs.
  • Graphics are also often described by the number of bits used to represent each dot. A 1-bit image is monochrome; an 8-bit image supports 256 colors or grayscales; and a 24- or 32-bit graphic supports true color.
How fast a modem can transmit and receive data. At slow rates, modems are measured in terms of baud rates. The slowest rate is 300 baud (about 25 characters per second). At higher speeds, modems are measured in terms of bits per second. The fastest modems run at 57,600 bps, although they can achieve even higher data transfer rates by compressing the data.

The Mosaic browser, circa 1993.

A Web browser is a software application used to locate and display Web pages. Popular browsers include Netscape Navigator, Microsoft Internet Explorer, Foxfire and Safari. All are graphical browsers, meaning they can display graphics as well as text. Most modern browsers also can present multimedia information, including sound and video, though they require plug-ins for some formats.
Abbreviation for binary term, a unit of storage capable of holding a single character. On almost all modern computers, a byte is equal to 8 bits. Large amounts of memory are indicated in terms of kilobytes (1,024 bytes), megabytes (1,048,576 bytes), and gigabytes (1,073,741,824 bytes).
Distinct pieces of information, usually formatted in a special way. All software is divided into two general categories: data and programs. Programs are collections of instructions for manipulating data. Data is the plural of datum, a single piece of information. The term data is often used to distinguish binary machine-readable information from textual human-readable information. For example, some applications make a distinction between data files (files that contain binary data) and text files that contain ASCII data.
Digital Subscriber Lines, the two main categories being ADSL and SDSL. Two other types of DSL technologies are High-data-rate DSL (HDSL) and Very high DSL (VDSL). DSL technologies use sophisticated modulation schemes to pack data onto copper wires. They are sometimes referred to as last-mile technologies because they are used only for connections from a telephone switching station to a home or office, not between switching stations. DSL is similar to ISDN in that both operate over existing copper telephone lines (POTS) and both require the short runs to a central telephone office. But DSL offers higher speeds.

A GIF file displaying 256 colors.

Graphics Interchange Format, a bit-mapped graphics file format used by the World Wide Web, CompuServe and many bulletin board systems. GIF supports color and various resolutions. It also includes data compression, but because it is limited to 256 colors, it is more effective for images such as illustrations rather than color photos.
HyperText Markup Language, the authoring language used to create documents on the World Wide Web. HTML is similar to SGML, although it is not a strict subset. HTML defines the structure and layout of a Web document by using a variety of tags and attributes. Hundreds of tags used to format and layout the information in a Web page. Tags are also used to specify hypertext links.
Internet Access Providers. See ISP.
Internet Message Access Protocol, an e-mail protocol newer than post office protocol.
A global network connecting millions of computers. More than 100 countries are linked into exchanges of data, news and opinions. The Internet is decentralized by design. Each Internet computer, called a host, is independent. Its operators can choose which Internet services to use and which local services to make available to the global Internet community. Remarkably, this anarchy by design works well. Note that Internet is not synonymous with World Wide Web.
Integrated Services Digital Network, an international communications standard for sending voice, video and data over digital telephone lines or normal telephone wires. ISDN supports data transfer rates of 64 Kbps (64,000 bits per second). Another version, called B-ISDN, uses broadband transmission and is able to support transmission rates of 1.5 Mbps. B-ISDN requires fiber optic cables.
International Organization for Standardization. Note that ISO is not an acronym; the name derives from the Greek word iso, meaning equal. Founded in 1946, ISO is an international organization composed of national standards bodies from more than 75 countries. For example, the American National Standards Institute is a member of ISO. ISO has defined a number of important computer standards, the most significant of which is perhaps Open Systems Interconnection (OSI), a standardized architecture for designing networks.
Internet Service Provider, a company that provides access to the Internet. For a monthly fee, the service provider gives you a software package, username, password and access phone number. Using a modem, you can log on to the Internet and browse the World Wide Web and USENET, and send and receive e-mail. ISPs also serve large companies by providing a direct connection from the company's networks to the Internet. ISPs themselves are connected to one another through Network Access Points. ISPs are also called IAPs (Internet Access Providers).

A JPG file displays 16,777,216 colors.

Joint Photographic Experts Group, the original name of the committee that wrote the standard. JPG is one of the image file formats supported on the Web. JPG is a lossy compression technique that is designed to compress color and grayscale continuous-tone images. The information that is discarded in the compression is supposed to be information that the human eye cannot detect. JPG images support 16,777,216 colors and are best suited for photographs and complex graphics. The user typically has to compromise on either the quality of the image or the size of the file. JPG does not work well on line drawings, lettering or simple graphics because these images do not have a lot of information that can be thrown out in the lossy process, so the image loses clarity and sharpness.
Multipurpose Internet Mail Extensions, a specification for formatting non-ASCII messages so that they can be sent over the Internet. Many e-mail clients now support MIME, enabling them to send and receive graphics, audio and video files via the Internet mail system. In addition, MIME supports messages in character sets other than ASCII.
Modulator-demodulator, a device or program that enables a computer to transmit data over telephone or cable-television lines. Computer information is stored digitally, whereas information transmitted over telephone lines is transmitted in the form of analog waves. A modem converts between these two forms.

PNG files support an alpha channel that can be used to add transparency to parts of the image.

Portable Network Graphics, a graphics standard supported by the Web though not supported by all browsers. PNG was developed as a patent-free answer to the GIF format but is also an improvement on the GIF technique. An image in a lossless PNG file can be 5 percent to 25 percent more compressed than a GIF file of the same image. PNG builds on the idea of transparency in GIF images and allows the control of the degree of transparency, known as opacity. Saving, restoring and re-saving a PNG image will not degrade its quality. PNG does not support animation as GIF does.
Post Office Protocol, a protocol used to retrieve e-mail from a mail server. POP comes in two versions: POP2 became a standard in the mid-1980s and requires SMTP to send messages. A newer version, POP3, can be used with or without SMTP.
Point Of Presence, an access point to the Internet. ISPs have typically multiple POPs. A point of presence is a physical location, either part of the facilities of a telecommunications provider that the ISP rents or a separate location from the telecommunications provider. The point of presences houses servers, routers, switches and other equipment.
Plain Old Telephone Service, the standard telephone service that most homes use. Those using POTS to access the Internet through a modem are said to have dial-up service, as compared with high-speed digital communications lines, such as ISDN and FDDI. POTS connections generally are restricted to about 52 Kbps (52,000 bits per second). The POTS network is also called the public switched telephone network.
A hardware or software module that adds a specific feature or service to a larger system. The idea is that the new component simply plugs in to the existing system. For example, a number of plug-ins are available for Web browsers that enable it to display different types of audio or video messages. Navigator plug-ins are based on MIME file types.
An organized list of instructions that, when executed, causes the computer to behave in a predetermined manner. Without programs, computers are useless.
  • A program is like a recipe. It contains a list of ingredients called variables and a list of directions called statements that tell the computer what to do with the variables.
  • Eventually, every program must be translated into a machine language that the computer can understand. This translation is performed by compilers, interpreters and assemblers.
Simple Mail Transfer Protocol, a protocol for sending e-mail messages between servers. Most e-mail systems that send mail over the Internet use SMTP. Messages can be retrieved with an e-mail client using either POP or IMAP. SMTP is usually used to send messages from a mail client to a mail server. This is why you need to specify both the POP or IMAP server and the SMTP server when you configure your e-mail application.
Standard Generalized Markup Language, a system for organizing and tagging elements of a document. SGML was developed and standardized by the International Organization for Standards (ISO) in 1986. SGML itself does not specify any particular formatting; rather, it specifies the rules for tagging elements. These tags can then be interpreted to format elements in different ways.
  1. A group of interdependent items that interact regularly to perform a task.
  2. An established or organized procedure; a method.
  3. A computer system refers to the hardware and software components that run a computer or computers.
  4. An information system is a system that collects and stores data.
  5. On Macintoshes, System is short for System file, an essential program that runs whenever you start up a Macintosh. The System provides information to all other applications that run on a Macintosh. The System and Finder programs together make up the Mac OS.
  6. System often simply refers to the operating system.
A command inserted in a document that specifies how the document, or a portion of the document, should be formatted. Tags are used by all format specifications that store documents as text files. This includes SGML and HTML. In html coding, a tag begins with < and ends with >. The information in between includes the tag itself first, followed by attributes that further define the tag.
Words, sentences, paragraphs. This page, for example, consists of text. Text processing refers to the ability to manipulate words, lines and pages. Typically, the term text refers to text stored as ASCII codes — that is, without any formatting. Objects that are not text include graphics, numbers if not stored as ASCII characters and program code.
World Wide Web
A system of Internet servers that support specially formatted documents. The documents are formatted in HTML and support links to other documents, as well as graphics, audio and video files. This means you can jump from one document to another simply by clicking on hot spots. Not all Internet servers are part of the World Wide Web. To access the Web, a program called a browser is used. Popular browsers include Netscape Navigator, Microsoft Internet Explorer, Foxfire and Safari. World Wide Web is not synonymous with the Internet.