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If you do get stuck, whether by being experimental or just by accident, it is helpful to remember a few points:
o You can always disconnect from a remote service by using your communications software to "hang up".
o If the computer gives you a strange symbol like a percent sign or a dollar sign and just sits and stares at you, you can try "help" or "?"
to try to find out what the computer expects, or else try "exit", "quit", "bye", "logoff", or something similar, to return to where you were before.
o Many times, when you log on to a system, you will get instructions on how to get further help or how to "escape" back to your own system.
You should remember these or write them down!
o As a last resort, exit the communications program (and all other active programs) and shut off your computer, turn off your modem, and disconnect it from the phone line. Be sure to do these steps in the order prescribed. It is unwise (though tempting) to simply turn your computer off and on, or to pull the plug on your modem with your computer running.
More suggestions for the inexperienced are given in Appendix A.
The final hurdle to using the Internet is that the world, even the world of the Internet, is indeed a very large place. When using the Internet you have to decide:
o where to go;
o what information you want (and where it might be); and
o how to get to it (and get it back home intact).
For a system as vast as the Internet, these are hard decisions. Often, the only strategy that works is to explore and try different things.
This course is designed to get you over the initial hurdles, give you a fair grounding in methods that work, and point you in the right direction. The exploration is up to you. As an initial orientation, we describe the "three worlds of the known Internet" in the next section.
The Internet, like ancient Gaul, is divided into three parts. These parts are not so much territories as worlds, each with their own sets of a.s.sumptions, favorite dialects, and favored equipment. We may conveniently refer to them as the "PC world", the "UNIX world", and the "Mainframe world". Here's a dossier on each of the three worlds: World: Personal Computer (PC) Typical Equipment: IBM PC and clones (85%) , Macintosh (15%) Conventional Operating Systems: MS-DOS, OS/2 Windowing Systems: Windows, MacOS Typical Size: PC ($1k to $5k typical; few $100 used) Clientele: Mixed--Business, Home users, just about everybody World: (mostly UNIX) workstation Typical Equipment: Sun Workstation, VAXStations, other vendors Conventional Operating Systems: UNIX (two major dialects), VMS Windowing System: X Windows Typical Size: Workstation ($5k and up) Clientele: Engineering/Scientific users; more and more businesses World: Mainframe or Minicomputer Typical Equipment: IBM (various), Digital Equipment VAXes Conventional Operating Systems: VM, VMS, UNIX Windowing Systems: X Windows, if available Typical Size: Minicomputer or Mainframe ($10k to millions) Clientele: Big Business, Universities, Government The neat picture of three worlds is distorted somewhat by a tendency for each of the worlds to have two (or a few) major options, either in choice of equipment, operating system, or vendor. So, for example, the PC world is split into two camps, the MS-DOS people and the Mac people. Similarly, the UNIX world is split into the "BSD" workstations and "System V" (i.e. "5") workstations. The three worlds are reflected somewhat in networking. The Internet is dominated by minicomputers and workstations running UNIX and VMS, with an ever increasing influx of PCs running MS-DOS and Macs. Machines running other operating systems often put a "UNIX-like" foot forward, so the user can almost believe he or she is dealing with UNIX machines. There is a certain sense that the UNIX software is the standard for the Internet. Software tends to appear on UNIX machines first and then be "ported" to other machines. What makes it possible for all these disparate machines to talk to each other is the "Internet Protocol" (known more formally as TCP/IP, for Transport Control Protocol/Internet Protocol). TCP/IP can be thought of as a set of rules for two computers to use when they communicate with each other, even if they are not from the same vendor. We are used to thinking of computer systems as having "software" and "hardware", but it is closer to the truth to say that complicated systems like the Internet have many levels--in the case of the Internet as many as seven--ranging from "very software" to "very hardware". Each level has its own set of rules, called its protocol. The TCP/IP protocol belongs to two of the middle levels. At the moment, the most common protocol for the two most "very hardware" levels is "Ethernet" (looks rather like the coaxial cable used for cable TV), while the "very software" levels are completely dependent on the vendor. In fact, it is this profusion of levels which lets the Internet work on just about any kind of hardware and with software from many different vendors. Anyway, the Internet grew up as several medium-sized networks, all having diffent "very hardware" and "very software", but using the TCP/IP protocol for their middle layers, were connected together. Two of the first, and biggest, nets to adopt the Internet Protocol were ARPAnet-- Internet was first designed for this one--the network for what used to be called DARPA (the Defense Advanced Research Projects Agency of the U.S. Department of Defense), and NSFnet, a network connecting universities and government laboratories for the U.S. National Science Foundation. These and other large networks form the "backbone" of the Internet. But today there are hundreds of smaller nets hooked on to the backbones. There *are* big networks that don't use TCP/IP. For example, in the context of IBM mainframes at large universities and research inst.i.tutions, BITnet (The "Because It's Time" Network) emerged. This large worldwide network does not use the Internet protocol. BITnet can be reached from the Internet through special translators called gateways, but it is definitely a different network. Occasionally one encounters problems that can be traced to this fact. The future of any technology is difficult to forcast, and I do not profess to know what the future holds for the Internet. Some predictions that various forcasters have made for internetworking (and telecommunications in general) are: o A proposal for a data "superhighway" called the NREN (National Research and Education Network) will pa.s.s the U.S. Congress. This is an upgrade for the Internet. o Commercial use of the Internet will become more common and new schemes for charging for its use will emerge. o The Internet will be handed by the government over to AT&T and the other "telecoms", who will charge so much to access it that the whole scheme will collapse. o Optical Fiber will replace Coaxial Cable (Ethernet protocol) as the most common standard for LANs. o The Internet will enter the home over ordinary phone lines. o The Internet will enter the home over existing Cable TV coaxial cable. o The Internet will enter the home through newly strung optical fiber as part of a unified system for Telephony, Cable TV, and the data communication, using [insert your favorite protocol here] as a standard. o Personal Computers will replace telephones, answering machines, stereos, CD players, and VCRs--maybe even TV!--as a single, universal device for home use. Sounds like a good thing to connect to the NREN. o Computer and telephone technology will become so intertwined that it is hard to tell the difference. One product, already on the market, is described as "[a handheld] alphanumeric pager, an XT-compatible computer with a backlit screen and PCMCIA Type III slot, a fax/modem, a cellular and land-line phone, and a voice recorder"! You are welcome to believe all or none of these predictions. Connecting to the Internet involves several steps: (1) Getting your modem and communications software working together (2) Connecting to a provider over the phone lines (or a LAN) (3) Using Internet services For the first step you will have to rely on the manuals that came with your modem and software. Appendix B contains a discussion of some of the obscurer terminology a.s.sociated with modem settings. You might want to read it if your manual is not well written. Actually, you do not have to know about the second step in great detail. Mostly it is a matter of knowing enough to intellegently choose a provider. Each provider will have a specific set of steps--modem settings, access numbers, pa.s.swords, etc.--that you need to follow in order to get from you to the provider. Don't lose hope! Once you get there you've finished the hardest part. Chapter 6 contains very explicit instructions for connecting to one particular service, DELPHI. Step 3 is the subject of the rest of this course--what you can do once you're on. The basics are discussed in the next chapter. In theory, there are three ways to connect to the Internet from a personal computer or workstation:
