By using Telnet, you can login to a computer anywhere on the Internet and use that computer as if you were sitting right next to it. Almost all services that the remote computer usually offers are available to you. The processing of your commands is done at the remote computer, and only keystrokes and the terminal output are passed along through the Internet. If you want to use Telnet, you usually have to have a valid account on the computer you want to connect to. Some sites offer special services such as current weather conditions and do not require a personal account.
I often use Telnet to connect to my `home' account and read electronic mail when I am away for a conference.
By using Ftp (File Transfer Protocol), you can copy files between any two computers on the Internet. You can login to a remote computer and then copy a file from there to your machine, or visa versa. If you have a valid account on the machine you connect to, you usually have access to all files you normally have access to. Many sites, however, offer the possibility of an anonymous connection. Only selected files will be accessible to you in this situation. Often shareware computer programs or documents of general interest are placed on an anonymous site and can then be copied by anyone on the Internet.
I used Ftp to transfer computer pictures about dynamical systems with a colleague, and I often use Ftp sites that allow anonymous access to obtain new software (such as the programs described here).
Usenet can be thought of as a collection of topics, called groups, ranging from the bizarre to the scientific. In each group, notes are placed by individuals, universities, companies, or governmental organizations. You can read these notes, download them, and, if you like, reply to them. Some notes may contain questions, some answers to previous notes or information of general interest to a group, and some may even contain complete computer programs or pictures. Before reading any of these notes, you have to decide which topics are of interest to you and `subscribe' to them. Some of the groups have a moderator who decides which notes should be posted, but most are freely accessible for posting.
As an example, I have subscribed to the groups sci.math (general discussions about mathematical questions for novices as well as mathematicians), sci.math.research (discussions about mathematical research), comp.binaries.ibm.pc (computer programs for MS-DOS based computers), and comp.binaries.mac (computer programs for Macintosh computers). On an infrequent basis, I read the discussions taking place in these groups, and occasionally obtain a useful computer program that way.
The Internet Gopher protocol and the first Gopher software was developed by the Gopher Team at the University of Minnesota. It was originally created as a fast, simple, distributed, campus-wide information search and retrieval system. Ease of use and implementation has made Gopher increasingly popular on the Internet. Since its original release, many folks on the Internet have contributed to its growth, submitting patches, servers, clients, and linking their local servers into the worldwide network of Gopher servers. Now there are even gateways to seamlessly access a variety of non-Gopher services such as FTP, Archie, WAIS, USENET news, whois servers, etc.(...) This network of Gopher servers is at your disposal from a Mac, PC, or workstation connected to the Internet.
(from documentation of TurboGopher)Gopher is a picturesque description of a method for placing and gathering information across the Internet. Universities or companies around the world decide on information which they think may be desirable for users to have and place this information under the guidance of a computer program called a Gopher server. A user can access that information by using another computer program called a Gopher client. Using such a Gopher client, you see a hierarchical list of topics, documents, pictures, programs, and other information, and you choose from that information what you like to obtain. The beauty of the Gopher system is that it shields the users from most of the complexities of the Internet. You can, for example, connect to the University of Minnesota's Gopher server, read an on-line help document about Gopher Services, then display a satellite picture of last week's weather over North America, next read information about grants offered by the NSF, then search the Library of Congress for exact references, and finally search the Internet for any references to symbolic math. You do not need to know where the information is actually located, or what type of information is offered. The Gopher server-client model will take care of everything.
The client-server model is a commonly used method of providing services over a network. The end-user uses a client program to access information by communicating with a server program. Typically the server and client are running on different machines and communicate over the network. You need not have a server of your own to be able to use the client.
The full-text database is a model designed explicitly to search documents on any word that appears in those documents. The old approach was to have a set of keywords which you could search on, and these words represented a small subset of all the words in the documents.
(Torkington: WAIS Introduction)WAIS (wide-area-information-system) is related to Gopher in that it shields the user from the intricacies of the Internet. You can view pictures, read documents, or obtain programs with a single keystroke, without knowing where the document is located or what type of document it is. However, rather then maneuvering through a hierarchical menu structure, and only occasionally using key-word searches, WAIS is based on a search mechanism from the beginning. You enter the information you are looking for in an English sentence, and WAIS does its best to locate information relating to your sentence. You usually start with a broad topic and refine your search as it progresses. The nice feature of WAIS based searches is that you don't need to enter an exact keyword. WAIS services usually give you an `index of matching', based on how well the found document agrees with your search specification (in WAIS's opinion). You can then continue to search only those hits with a high index of matching, or decide to follow a new tangent.
Internet Relay Chat (IRC) is another server-client model, developed in Finland in 1988. You connect to a server and are then able to `talk' in real-time to other people connected to IRC. All discussions are divided into groups, called channels (private, public, moderated, secret, or open), and you have to join a channel before you can enter in a discussion. Once joined (and obtained permission to speak, if necessary), you can enter into discussions in real-time with any other person on that channel. The other members could be located on your campus, in North America, or in any of 20+ countries of the world. Everything that is typed by any member of a channel is displayed almost immediately on every channel member's screen, allowing `party line' conversations around the world. You could start your own group and wait for other members to join, of you can join other groups. Your discussions could be designated as private (others can join by invitation only) or public (anybody can join).
Great groups to join are the Chess group, in which you may be challenged for a game of chess by a person in China, or - being German - I search out other people from Germany currently on IRC and talk for a while in German with them.
You invoke the program by telling it with whom you would like to talk. That person can be located next door or half way around the world. If the recipient is currently at a machine that has the Talk standard implemented, a message will appear on the screen, informing the person that someone would like to have a conversation. The person then issues his or her own version of the Talk command, communication is established, and both party's typing appears simultaneously on each screen.
The best method, however, for accessing a library is by using the Gopher software. Most gopher sites offer as one of their choices Library access, and list many, many libraries available for searching. For mathematics, the Gopher client of the AMS gives many mathematically oriented libraries and automatically connects you as well.
For example, you could automatically receive preprints of mathematical research papers and other material in Several Complex Variables about once a month to your electronic mail address. Many of the preprints could even be sent to you in their entirety (usually in TeX format) if you request it. That can cut down considerably on the time you need to learn about new results in that area. (The details of this particular service are currently being changed to allow Gopher access)