Southern Illinois University at Carbondale Information Technology

If you need to define a word, term, or acronym you can't find in this glossary, consult the online glossary at the Digital Reality site. You might also try Tech Web's Tech Encyclopedia or PONG, the PC World Online Glossary.

Account: When you use a particular computer system, you are given an account, which includes a unique user name and a password. You enter these when you login to the system. Some computer systems, like PCs that were designed to be used by a single user, assume that anyone using the machine is that user and do not allow formal accounts. With these machines, you may need an account on a different system to take full advantage of the services offered over the network. To get access to the computers maintained by Information Technology at SIUC, you will probably be using either a Network ID or a mainframe ID. Each has its own security criteria.

Address: A unique name or number identifying a specific computer. Addresses are used in network communications in transmitting messages to a particular machine. You can address a particular person by associating their account with the address of the machine where they have the account. For example, the "john" in john@reliant.c-cwis.siu.edu is the account of an individual on the machine "reliant.c-cwis.siu.edu". This machine address is an IP (Internet Protocol) address. IP addresses can also be expressed numerically, e.g., 131.230.73.55 represents the same machine. The verbal names are simply easier for people to remember.

ASCII: American Standard Code for Information Interchange. A standardized data encoding scheme introduced to achieve compatibility between unlike computing/transmitting machinery. A "plain ASCII" file typically contains only those characters on standard keyboards.

Binary File: Any file that is not a plain-text file is a binary file. When transferring these files, you must use binary mode to avoid strange changes to the file.

Browser: Software that lets you display text and images stored on "pages" around the Internet. Examples include Netscape, Mosaic, and Microsoft's Internet Explorer.

CAN: Campus Area Network. This is the fiber-optic cable "backbone" linking campus buildings to each other and to external networks like the Internet.

Client/Server: A computing paradigm that divides the workload between client software, usually stored on your desktop computer, and server software, usually stored on a remote computer elsewhere on campus or anywhere in the world. (See the definition of "remote" below.) The client portion on your desktop usually lets you customize screen fonts, colors, which programs interpret sounds and images, and so on. The word "server" is currently used to describe both the software that communicates with clients and the computer it resides on. Typically, the client on your desktop computer sends a request to a server over whatever network(s) are involved, the server responds to the request (e.g., a file server may download a file), and then breaks the connection with your client and responds or awaits the next client's request. The process is "transparent" to users, meaning these intercomputer communications are hidden from you. The client-server paradigm is discussed in greater detail in a supporting document.

Database: A collection of information organized around a common subject. An example might be a set of cards containing names, addresses, birthdates and other personal information, one person per card, sorted by last name. Keeping such information on a computer in electronic format allows the database application program to re-sort the entries by any of the criteria contained in the set of data ("Sort by last name," "Sort by City," "Sort by State," using the note card 'database' example). Using a computer to hold such information gives the capacity for nearly instantaneous searches for specific pieces or subsets of information, and the efficient generation of reports containing defined subsets of the data ("Find all persons in the database born in June," or or "Find all entries where the 'First Name' is 'Arnold' and the 'Date of Birth' is February" for example).

Domain Name (or Domain Name System, DNS: A system for delegating address authority. To address a unique machine, a unique address is needed. Since any machine may be connected to a network that is worldwide, this address must be globally unique. It would be impossible for any single agency to directly administer all these addresses around the world. The Domain Name System establishes a separate domain for each country. Within each country, separate domains are established for each organization (academic, corporate, governmental, etc.). Within each organization, separate subdomains are established. Typically, the address of a machine is a list of the domains it is a member of, separated by periods. The most common domain names are:

.com is used for most businesses/commercial sites

.org is used for organizations

.edu is used for educational organizations

.gov is used for nonmilitary US government sites

.mil is used for US military sites

.net is used for Net service providers

Some of the more common foreign domains are identified by the following:

ca Canada

fr France

ru Russia

es Spain

ni Nicaragua

uk United Kingdom

fi Finland

mx Mexico

us United States

DOS: Disk Operating System. An operating system (the OS in DOS) is the interface between human and microprocessor (or "chip"). It translates the commands you type in into the machine language the microprocessor speaks. DOS was developed by Microsoft in the early 1980s for the Intel processor. Today, such popular graphic "shells" like Microsoft's Windows and IBM's OS/2 run on top of DOS.

Download: Transmitting information "down" from a remote computer. The term is a leftover from the mainframe computing paradigm, wherein a massive central host computer transmitted files "down" to a small, "dumb" terminal. The vertical nature of the term is meaningless now, since some microcomputers are more powerful than mainframes, and file sharing now takes place between "parallel" equals in the client/server paradigm. In the most common file transfer protocol (FTP), the command to "download" a file actually is GET, which gets a copy of a file from a remote host and stores it on your local machine. You can read more about FTP in a separate document.

E-Mail: Electronic Mail. An electronic way to exchange notes, documents, and other data between users of the same or different computing systems. E-mail delivery is divided into two portions: a delivery agent and a user agent. The delivery agent uses SMTP (Simple Mail Transfer Protocol) to route mail between "post offices." The user agent is used by the user to access their own mail from a post office and display it for reading. It is also used to create and send e-mail. Popular user agents include Eudora, NuPOP, Elm, and PINE. We discuss electronic mail in greater depth in other documentation.

Flow Control (XON/XOFF): This modem feature often reserves certain control characters (i.e., CTRL+c, CTRL+s, etc.) that lets the communications software manage the flow of data between your computer and the remote computer. These control characters are also used by many programs, such as the Emacs editor. If your modem has XON/XOFF turned on, it will intercept these control characters and prevent them from being sent to the file you are trying to edit.

FTP: File Transfer Protocol. An executable program (or a command) that handles the details of connecting with and retrieving data from remote servers. The FTP and Telnet commands are the two most important included in the TCP/IP (Transfer Control Protocol/Internet Protocol) communications software.

Gateway: A connection between two networks. The connection may be between physical networks, logical networks, or network services.

Home Page: The beginning page or document specified in a URL. For example, www.siu.edu points to SIUC's home page; www.siu.edu/cwis points to the CWIS team's home page. Other pages are pointed to from the home page.

Host: Another name for a computer. This name originated when the only computers were big computers with many users connected to them. In that context, "host" made sense, since the big computer (e.g., a mainframe) "hosted" all users. In a modern, peer-to-peer network like the Internet, every machine is a peer. Therefore, in a modern network, every machine is also a host and "hosts" one or more users.

Hypertext: This concept has actually been around more than fifty years. Hypertext is text that contains links (often called "hotlinks") from words or phrases to other documents that elaborate, explain, or otherwise follow a thought embodied in the linking word or phrase. For example, we might highlight the word "links" above. Clicking on that word would then connect you--via the HyperText Transport Protocol (HTTP)--to a fuller discussion of the linking concept in a separate document. This second document might reside on your own computer or on a computer half a world away. Note that our definition of "document" includes text, images, sound, and video in any combination.

Internet: A global network of networks. The SIU campus network is a part of the Internet, and all Internet services are available on campus. To use Internet services you must have TCP/IP network software on your machine. This is the common language that lets data be transferred between unlike computers. Internet services are also available on the SIU dial-up at (618) 453-3500. To dial-up, you must also have SLIP (Serial Line Interface Protocol) or PPP (Point-to-Point Protocol) software on your machine (both are usually included in the TCP/IP suite).

IRC: Internet Relay Chat. This service lets groups converse with each other in real time across the Internet. It is a sort of e-mail facility with a built-in broadcast function that automatically sends your message to other users logged into the same discussion. Some call it the keyboard equivalent of Citizens Band radio.

ISP: Internet Service Provider. An organization, such as a private business or an educational institution, that provides a linkage to the Internet "backbone."

LAN: Local Area Network. Typically, a group of microcomputer users, such as a department or building, whose workstations are linked together to share resources. A LAN at SIUC is usually connected to the CAN, which is a part of the Internet.

Listserv:A listserv maintains a mailing list of subscribers. Whenever a query or comment is sent to the listserv, the listserv e-mails a copy to each subscriber. This is a good way to disseminate information when the subscribers want all comments and are scattered around the world. This function has been largely supplanted by news groups on the Internet. SIUC once ran a listserv on its mainframe computer; it has since been moved to a Unix-based server. You can read about the how to join the listserv at this link.

Logon/Login: A system for identifying yourself as a valid user of the system. This is done by entering your account information (ID and password) when requested by the host. The exact form of the request varies from host to host.

Logoff/Logout: A procedure for terminating an interactive session on a host computer that was initiated with a login/logon procedure. This frees all the resources that you were using and makes the connection available to another user. Failure to logoff/logout after a session means your session will most likely terminate abnormally, which may cause loss of data or work.

Mainframe: This word represents an entire computing paradigm. Typically, mainframe computers are very large, are housed in a central, secure location, and offer memory and disk-storage capacities that desktop microcomputers heretofore could not match. Historically, SIUC mainframes have been set up to handle (1) noninteractive (sometimes called "batch") computing jobs through the Multiple Virtual Storage (MVS) operating system and (2) multiuser, interactive computing through networked workstations and dumb terminals. Microcomputers have shrunk in size, dropped in price, and grown in memory and disk capacity, and they now approach the power, speed, and capacity of high-end mainframes. The time-sharing paradigm used by the mainframe has been replaced with the client/server paradigm.

Modem: MOdulator/DEModulator. This piece of hardware and the software that drives it allows computer data to be transmitted over telephone lines originally designed to carry only voice signals. A modem modulates your computer's electronic signals and sends it out through your telephone line, and a modem on the receiving computer demodulates the signals back into data it can read.

Multimedia: Programs synchronize multiple media and play them back on your computer screen. Typically, sound, images, animated sequences, and text are read from CD-ROM disks and are simultaneously reproduced on your computer screen. Multimedia transforms your computer into a "smart television," allowing you to stop, start, or save to disk information as it appears on your screen.

Nameserver: Each machine on the Internet must have a unique address. The Internet stores this address as a number, e.g., 131.230.73.55. This number is difficult for people to work with, however, so a verbal version of each numerical address is also created, e.g., reliant.c-cwis.siu.edu. When you use this name, such as to send e-mail to john@reliant.c-cwis.siu.edu, it must be matched with the numerical address the computer understands. In the early days of the Internet, a "look-up" table was stored on each machine. Now, a nameserver is assigned for each LAN. This nameserver knows about its own network. Each nameserver knows about a domain nameserver that it goes to for addresses it does not know. The domain nameserver in turn knows about the master servers for the Internet. When you use an address that your local nameserver does not know, it forwards the request to the next-higher level of nameserver, until the server is found that is responsible for addresses in that local network.

Network: Interconnected computers. Three networks have already been defined here: the LAN, the CAN, and the Internet. Sometimes the term WAN (Wide Area Network) is also used. The size of the network may vary, but the critical element is the communication protocol used to allow different types of computers to exchange messages and data. Two computers may be on the same physical network, but they can't "see" each other unless they are using the same network protocol (see the Protocol definition below).

NFS: Network File System. This is a virtual disk storage system that uses TCP/IP protocol to allow computers on a network to share files and disk space in such a way that it appears to the user as a single, seamless file system.

OS/2: IBM's GUI (Graphical User Interface) operating system. It provides mouse-selectable (point-and-click) icons and menus and data-sharing between applications.

Protocol: Communication rules or language. When computers communicate, their messages must be put into a "packet" or envelope that both can recognize. These envelopes, like the postal envelopes we are familiar with, must carry a return address and a destination address. The protocol determines how and where these addresses appear within the packet. If the sending and receiving protocols are not the same, the receiving machine will get the wrong address information from the packet and fail to recognize its own messages. Some protocols in use at SIU are TCP/IP (Internet protocol), SNA (IBM mainframe protocol), IPX (Novell netware protocol), DLR (DOS LAN Requestor), and LocalTalk (Apple/Macintosh protocol). TCP/IP mediates communication between these different protocols across the Internet. This explains why your Macintosh cannot talk to a DOS server or why you cannot talk to the Internet without TCP/IP.

Remote: This word is often used in phrases like "remote computer" or "remote host." In essence, it means a computer other than the one your keyboard is physically connected to. The distance implied in the word "remote" is misleading, because the other machine may be anywhere. Network tools, like Telnet (defined below), can make it seem to you as if your keyboard were directly connected to the other machine.

Server: See "Client/Server" above.

Spreadsheet/Worksheet: Applications, such as Lotus 1-2-3 or Excel, that allows you to enter data into amatrix of columns and rows and manipulate it according to formulas of your choosing.

TCP/IP: Transfer Control Protocol/Internet Protocol. This is the communications protocol suite used by the Internet (see Internet and Protocol above). A supporting document dicusses TCP/IP in detail, including a brief history.

Telnet: One of the executable programs usually included in a TCP/IP software package. This is an Internet terminal emulation service for machines other than IBM mainframe-type machines. Telnet is now deprecated and should not be used if it is at all possible to avoid it. Telnet has been superceded by "Secure SHell" or "SSH," for reasons of data security and privacy. Typically, telnet is the terminal emulation you use to access a remote system running a Unix operating system variant. This terminal emulation uses the ASCII standard for encoding information. It manages the details of logging in to a remote computer and interacts with it as if your keyboard and monitor were directly attached to the remote computer. It emulates older-style nongraphics terminals but is still valuable because it uses so few network resources and allows you to work effectively on distant machines. See the VT100 definition below.

tn3270: A special Telnet program that emulates the special terminals used by IBM mainframe-type computers. It emulates terminals in the IBM 3270 series that use the EBCDIC (Extended Binary Coded Decimal Interchange Code) standard for encoding information instead of the ASCII encoding format.

Unix: An interactive operating system developed at Bell Labs. This is the first operating system that wasdeveloped as a portable system. This allows Unix to be used as an operating system on almost any kind of computer. For example, we have Unix operating systems for PCs, Macintoshes, Suns, and even IBM mainframes. TCP/IP was built into Unix even in its early days; the Internet was originally intended to connect different Unix systems into a network. This link points to an introduction and discussion of Unix.

URL: Uniform Resource Locator. A universal way of addressing sites and services around the Internet, e.g., http://www.siu.edu/.

Usenet: A worldwide Unix-based network that supports the distribution of messages. Like BITNET, Usenet is a "store-and-forward" protocol and has been largely supplanted by the Internet with its real-time capability.

VT100: An ASCII terminal manufactured by Digital Equipment Company (DEC). This was a very popular terminal in the 1960s and 1970s for use with Unix and other non-IBM systems. Since almost every computer made could recognize and work with a VT100 terminal, all the terminal emulation products designed to work with non-IBM computers offer a VT100 emulation. It has become the de facto "lingua franca" of terminals.

Windows: Microsoft's GUI (Graphical User Interface) that surrounds the DOS operating system. Like other GUI interfaces, such as IBM's OS/2, Unix's XWindows, and the Macintosh Operating System, Windows allows mouse-selectable icons and menus and data-sharing between applications.

Winsock: This is short for "Windows Sockets API (Application Programming Interface)." This program creates a protected "socket" of memory in your computer, from which it manages transactions between Windows applications and the Internet. Much more detailed information in the FAQ format can be found at the following remote site, http://www.well.com/user/nac/alt-winsock-faq.html.

Word Processor: A computer program to manipulate text. A word processor can create, edit, and format electronic documents easily.

World Wide Web (WWW): This is a hypertext system that allows any document to refer to other documents anywhere on the Internet where there is a World Wide Web server. To use the World Wide Web, you need a WWW Browser (e.g., Netscape or Internet Explorer). This application knows WWW protocol and the name of at least one WWW document. When you start the application, it accesses that document. That document, in its turn, provides links to other documents that are available on the Internet. Most browsers provide multimedia capabilities and can display formatted text, images, and sounds.

Glossary of Computing and Telecommunication Terms