A computer is a general purpose electronic machine that can be instructed to do a great variety of things - play games, perform complex calculations, store and retrieve information, display graphs and so on.
You can ask a computer to do things directly - by typing commands on its keyboard - but for complex tasks, a whole series of instructions is usually written and stored in the computer's memory. The computer can be instructed to call up these instructions one by one and carry them out, very fast. (Your Electron can carry out, or 'execute', over 250,000 separate instructions every second.)
A series of instructions like this is called a program. Programs can be recorded onto cassette by using a suitable cassette recorder in much the same way as you might record a piece of music. The main difference is that the recording is made from a computer, and is played back into the computer again. You can buy pre-recorded programs which have been written by other people, and to start you off, several programs are provided on the Introductory Cassette which comes with your Electron.
The first part of this book describes how to set up your computer, and load and run the programs on the Introductory Cassette. For information on other programs available for the Electron (the general name for programs is 'software'), write to:
4a Market Hill
Cambridge CB2 3NJ
The remainder of this book (chapter 4 onwards), and the book Start Programming with the Electron, will tell you how to write your own programs on your Electron computer. You do not need to know this in order to use your computer, as there are many commercially available programs - but we hope that you will be interested and will want to find out more about your Electron.