Other computer owners never bother to learn beyond the rudiments of

programming. When they want software to catalogue their stamp collection,

they buy a pre-written program from a local shop or via mail order. Rather

than struggling to write a program to play noughts and crosses they prefer to

purchase complex games such as Elite, which have taken professional

programmers months to produce.

Some computer owners play the occasional game but primarily use the

computer for more serious purposes. They prepare and print out letters with

the help of a word processor, use spreadsheets to help them make financial

decisions, and store important information on disc.

The computer is a tool; complex and sophisticated, but a tool nonetheless. Do

not feel that you must learn to program to use it properly. Your computer

contains other powerful facilities which are described in later sections. A wide

range of software to meet virtually any need is available -- you do not need to

program to find the computer a valuable and useful aid.

The next few sections demonstrate some of the possibilities of programming.

They are intended only as an introduction to BASIC, but you will learn more

from them if you experiment with the example programs that are listed.

Change the values of the variables or add some lines of your own. Don't worry if

you make a mistake that seems to keep the program going forever. You can

always press which stops the program and brings back the > prompt to

show you can again input instructions.

Simple graphics

The computer provides eight different screen display modes and the Welcome

software showed you one of the most obvious differences between the modes --

the number of characters that can be displayed on .a line. The Welcome

software also demonstrated how some modes allow both the printing of text and

the display of graphics.

The modes differ in a number of important ways. Some of these differences will

be explained in this chapter, but a full list of the characteristics of the modes is

also provided in Appendix 1.

Two sets of modes are available, modes 0 to 7 and modes 128 to 135. Each

low-numbered mode N has a high-numbered counterpart mode N + 128 which

behaves visibly in exactly the same way and has the same features. For

example, mode 7 and mode 135 are identical in appearance.

You should use modes 0 to 7 if you are writing programs which may also be run

on the original BBC Model B microcomputer. In the Master Series computers,

modes 128 to 135 leave more memory free so that longer programs can be

written. For this reason you should always use the high-numbered modes but,

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