CSci 105

Introduction to Computers

Lecture 16

© Morris Firebaugh

I. Introduction

A. Conclude Chapter 5 -- Storage and Multimedia
B. Processing Stored Data
C. Introduce Chapter 6 -- Networking
D. History of the Net
E. How does it work?

II.Processing Stored Data

Three modes of processing data


Batch Processing


Transaction Processing


Combination Mode: Batch/Transaction


III. Introduce Chapter 6: Networking

History of the Internet

The Internet itself is the best source of information on the Internet



In the 1960s, researchers began experimenting with linking computers to each other and to people through telephone hookups, using funds from the US Defense Department's Advanced Research Projects Agency (ARPA).

ARPA wanted to see if computers in different locations could be linked using a new technology known as packet switching. This technology, in which data meant for another location is broken up into little pieces, each with its own "forwarding address" had the promise of letting several users share just one communications line. Just as important, from ARPA's viewpoint, was that this allowed for creation of networks that could automatically route data around downed circuits or computers. ARPA's goal was not the creation of today's international computer-using community, but development of a data network that could survive a nuclear attack.

Previous computer networking efforts had required a line between each computer on the network, sort of like a one-track train route. The packet system allowed for creation of a data highway, in which large numbers of vehicles could essentially share the same lane. Each packet was given the computer equivalent of a map and a time stamp, so that it could be sent to the right destination, where it would then be reassembled into a message the computer or a human could use.

This system allowed computers to share data and the researchers to exchange electronic mail, or e-mail. In itself, e-mail was something of a revolution, offering the ability to send detailed letters at the speed of a phone call.

As this system, known as ARPANet, grew, some enterprising college students (and one in high school) developed a way to use it to conduct online conferences. These started as science-oriented discussions, but they soon branched out into virtually every other field, as people recognized the power of being able to "talk" to hundreds, or even thousands, of people around the country.

In the 1970s, ARPA helped support the development of rules, or protocols, for transferring data between different types of computer networks. These "internet" (from "internetworking") protocols made it possible to develop the worldwide Net we have today that links all sorts of computers across national boundaries. By the close of the 1970s, links developed between ARPANet and counterparts in other countries. The world was now tied together in a computer web.

In the 1980s, this network of networks, which became known collectively as the Internet, expanded at a phenomenal rate. Hundreds, then thousands, of colleges, research companies and government agencies began to connect their computers to this worldwide Net. Some enterprising hobbyists and companies unwilling to pay the high costs of Internet access (or unable to meet stringent government regulations for access) learned how to link their own systems to the Internet, even if "only" for e-mail and conferences. Some of these systems began offering access to the public. Now anybody with a computer and modem, persistence and a small amount of money -- and persistence -- could tap into the world.

In the 1990s, the Net continues to grow at exponential rates. Some estimates are that the volume of messages transferred through the Net grows 20 percent a month. In response, government and other users have tried in recent years to expand the Net itself. Once, the main Net "backbone" in the U.S. moved data at 56,000 bits per second. That proved too slow for the ever increasing amounts of data being sent over it, and in recent years the maximum speed was increased to 1.5 million and then 45 million bits per second. Even before the Net was able to reach that latter speed, however, Net experts were already figuring out ways to pump data at speeds of up to 2 billion bits per second -- fast enough to send the entire Encyclopedia Britannica across the country in just one or two seconds. Another major change has been the development of commercial services that provide internetworking services at speeds comparable to those of the government system. In fact, what started as a government experiment is now largely a private enterprise.

IV. How Does It Work?

The worldwide Net is actually a complex web of smaller regional networks. To understand it, picture a modern road network of transcontinental superhighways connecting large cities. From these large cities come smaller freeways and parkways to link together small towns, whose residents travel on slower, narrow residential ways.

The Net superhighway is the high-speed Internet. Connected to this are computers that use a particular system of transferring data at high speeds. In the US, the major Internet "backbones" theoretically can move data at rates of 45 million bits per second (compare this to the average home modem, which has a top speed of roughly 28,800 to 55,600 bits per second). Connected to the backbone computers are smaller networks serving particular geographic regions, which generally move data at speeds around 1.5 million bits per second. Feeding off these in turn are even smaller networks or individual computers.

Unlike with commercial networks such as CompuServe or America OnLine, there is no one central computer or computers running the Internet -- its resources are to be found among thousands of individual computers. This is both its greatest strength and its greatest weakness. The approach means it is virtually impossible for the entire Net to crash at once -- even if one computer shuts down, the rest of the network stays up. The design also reduces the costs for an individual or organization to get onto the network. However, thousands of connected computers can also make it difficult to navigate the Net and find what you want -- especially as different computers may have different commands for plumbing their resources. It is only recently that Net users have begun to develop the sorts of navigational tools and "maps" that will let neophytes get around without getting lost.

Nobody really knows how many computers and networks actually make up this Net. The rapid growth in the number of Internet hosts over the past ten years is shown below:

The Net is more than just a technological marvel. It is human communication at its most fundamental level. The pace may be a little quicker when the messages race around the world in a few seconds, but it's not much different from a large and interesting party. You'll see things in cyberspace that will make you laugh; you'll see things that will anger you. You'll read silly little snippets and new ideas that WILL make you think. You'll make new friends and meet people you wish would just go away. And you'll do it all in a community that transcends state lines and national borders.

Major network providers continue to work on ways to make it easier for users of one network to communicate with those of another. Work is underway on a system for providing a universal "white pages" in which you could look up somebody's electronic-mail address, for example. This connectivity trend will likely speed up in coming years as users begin to demand seamless network access, much as telephone users can now dial almost anywhere in the world without worrying about how many phone companies actually have to connect their calls.

Today, the links grow ever closer between the Internet and such commercial networks as CompuServe and AOL, whose users can now exchange electronic mail with their Internet friends. All of the major commercial networks, such as CompuServe and America Online are gradually bringing internet access to their users (one network, Delphi, already offers complete access).

And as it becomes easier to use, more and more people will join this worldwide community we call the Net.

Being connected to the Net takes more than just reading conferences and logging messages to your computer; it takes asking and answering questions, exchanging opinions -- getting involved.

If you chose to go forward, to use and contribute, you will become a citizen of Cyberspace. If you're reading these words for the first time, this may seem like an amusing but unlikely notion -- that one could "inhabit" a place without physical space. But put a mark beside these words. Join the Net and actively participate for a year. Then re-read this passage. It will no longer seem so strange to be a "citizen of Cyberspace." It will seem like the most natural thing in the world.

And that leads to another fundamental thing to remember:

You can't break the Net!

As you travel the Net, your computer may freeze, your screen may erupt into a mass of gibberish. You may think you've just disabled a million- dollar computer somewhere -- or even your own personal computer. Sooner or later, this feeling happens to everyone -- and likely more than once. But the Net and your computer are hardier than you think, so relax. You can no more break the Net than you can the phone system. If something goes wrong, try again. If nothing at all happens, you can always disconnect. If worse comes to worse, you can turn off your computer. Then take a deep breath. And dial right back in. Leave a note for the person who runs the computer to which you've connected to ask for advice. Try it again. Persistence pays.

Stay and contribute. The Net will be richer for it -- and so will you.


V. E-Mail

Electronic mail, or e-mail, is your personal connection to the world of the Net.

All of the millions of people around the world who use the Net have their own e-mail addresses. A growing number of "gateways" tie more and more people to the Net every day.

The basic concepts behind e-mail parallel those of regular mail. You send mail to people at their particular addresses. In turn, they write to you at your e-mail address. You can subscribe to the electronic equivalent of magazines and newspapers. Sooner or later, you'll probably even get electronic junk mail.

E-mail has two distinct advantages over regular mail. The most obvious is speed. Instead of several days, your message can reach the other side of the world in hours, minutes or even seconds (depending on where you drop off your mail and the state of the connections between there and your recipient). The other advantage is that once you master the basics, you'll be able to use e-mail to access databases and file libraries.

E-mail also has advantages over the telephone. You send your message when it's convenient for you. Your recipients respond at their convenience. No more telephone tag. And while a phone call across the country or around the world can quickly result in huge phone bills, e- mail lets you exchange vast amounts of mail for only a few pennies -- even if the other person is on the other side of the earth.

E-mail is your connection to help -- your Net lifeline. The Net can sometimes seem a frustrating place! No matter how hard you try, no matter where you look, you just might not be able to find the answer to whatever is causing you problems. But when you know how to use e-mail, help is often just a few keystrokes away: you can ask your system administrator or a friend for help in an e-mail message.

How Can YOU use E-mail?

There are two easy steps:

  1. Login to get a LOGIN Name and Password
  2. Use the Mail option of your browser

1.  The steps to getting a LOGIN Name and Password are


 2.  Using NetScape Mail

VI. A Brief Tour of the Internet


Updated March 6, 2001