There's certainly a lot of interest in computers. Of course, they have become a very common thing. Pierre Kerr, ac210@freenet.carleton.ca, has been working with computers for twenty years. He gives the following answer.

I looked into the Compton's Interactive Encyclopedia to see what they had for a definition of a computer and this is what I found:

COMPUTER

Generally, any device that can perform numerical calculations-even an adding machine, an abacus, or a slide rule-may be called a computer. Currently, however, the term usually refers to an electronic device that can use a list of instructions, called a program, to perform calculations or to store, manipulate, and retrieve information.

In 1847, that's more that 140 years ago, a man named Charles Babbage designed something that he called "Difference Engine Number 2." His machine is considered to be the first computer. This machine could not be built, however, until 1991 because the gears and bearings were far too difficult to make in 1847. A working model was built by scientists at the Science Museum in London England and it worked perfectly. It also weighed as much as large car!

Before there were computers, scientists had to do calculations using printed tables of numbers. Often, these tables would have errors in them and so the results that the scientists got from their calculations also had errors. Charles Babbage once said to John Herschel, a famous British astronomer, after discovering an error in a printed table "I wish these calculations had been executed by steam!" Can you imagine a computer that ran on steam!

Today we're used to seeing a PC or personal computer, sitting on a desk and giving precise answers to our questions. There are, of course, much bigger computers that are used by large companies, governments and universities. These are called mini-computers or main-frame computers and they could be big enough to fill your school library.

The invention of the transistor in 1947 and later the integrated circuit or chip, helped to make the small powerful computers that are so common today. The transistor is an electronic switch and an integrated circuit can contain millions of transistors in a tiny square smaller than your baby fingernail.

A computer is actually a pretty simple device. It doesn't really do much more than:

Store a number into memory

Get a number from memory

Add two numbers and store the result in memory

Do comparisons between two numbers such as: are they the same, is the first bigger than the second, is a number equal to zero

Now, of course, a computer can do these things very quickly. This is what makes a computer seem smart. Also, the memory that the computer has can allow it to store a very large amount of information.

A computer is made of both hardware, the things you can touch, and software, commands that the computer understands.

Hardware

CPU - Central Processing Unit

This is the actual brain of the computer. It's the part that does the adding, storing, comparing and retrieving. These days, the CPU is just an Integrated circuit and doesn't look too exciting.

Memory

Memory is really only a bunch of switches that can be on or off. The computer sort of looks at the switch to see if it's on or off when it reads memory or flips the switch when it writes memory. Each switch is called a BIT and the computer usually looks at 8 bits at a time. Eight bits is called a BYTE. If the switch is on then it represents a value of 1, if it is off then it has a value of 0. Computers can only add ones and zeroes. The way they seem to add bigger numbers is done by clever programs.

Another type of memory is ROM or read only memory. This is also an integrated circuit but the computer can only read this information not change it. When you first turn on a computer it usually reads its first instructions from ROM. There is a special type of ROM called EPROM. The E stands for erasable. These memory chips can be erased if they are placed under a special light. The light shines through the tiny window in the chip and in a few hours will clear all of the memory. Information can then be stored in it again by using a special machine called an EPROM programmer.

There is yet another type of memory and it has many types. This memory is stored on external devices such as floppy disks, hard disks and tape drives. These days a CD or optical disk is becoming quite common as well.

There have been several questions about floppy disks and hard disks asked by other students at your school. Maybe they will share their answers with you.

Input/Output Devices

A CPU with memory wouldn't be very useful unless there was some way we humans could communicate with the computer.

The early computers had a lot of lights on them. These were fun to look at but not very practical. You've probably seen old science fiction movies where the computer is a wall of lights and buzzers. In the 1960's computers actually did look like this.

Later, electric typewriters were modified so that humans could type instructions using the keyboard and the computer would give the answers by typing on paper. These machines were called teletypes. The paper was replaced with a TV screen and these were called 'glass' teletypes. Today, almost all interaction with a computer is by using a keyboard and a TV screen or monitor. Output to paper is done using either printers that use ink and ribbon just like a typewriter or laser printers that work a lot like a photo-copier.

Software

As I'm typing these words on a computer, I don't have to worry about where each letter goes in the computer's memory or how to make the printer print it. I just do a human-like thing and type on a keyboard. It's software that takes care of all the details.

There are three different categories of software that could be running on the computer

Operating System

The very basic smarts of the computer come from a piece of software called the operating system. On the computer that I'm using it's called MS-DOS. It knows how to read and write to the disk drives, send information to the screen, send information to the printer and modem and receive information from the mouse and keyboard and modem. However, it doesn't know much about math or word processing.

Languages

On most computers, there are one or more computer interpreters or compilers that take human-like commands and turn them into computer instructions. BASIC is a very common computer language. Other languages are LOGO, FORTRAN, COBOL, APL, Pascal, C, assembler and Forth.

If you plan on learning more about computers, you will probably learn at least one computer language.

Applications

To be really useful to a lot of people, most computers come with one or more applications. This could include a word-processing program, a spreadsheet program or a graphics program.

You could also have very specific programs such as one that keeps track of students work or one that forecasts the weather or controls a space ship. Of course, where would we be without computer games. They're a type of computer application. They make humans happy and help sell more computers.

There's a lot more to say about computers, but you can find more information in your library. There has been a computer on the wall of your library showing all of it's bits and pieces. We hope you have had a good look. Thanks for your questions and your patience in waiting for the answer. Have a good summer

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