We have so far learned how to print stuff onto the screen and store numbers and text in variables. We are still a way off developing our version of “Angry Birds”, but we’re not far off…

One of the most important commands that a computer has is the “IF” statement. This allows the computer to make a decision.

By the way, have you noticed that BASIC can be read out like English; you can usually work out what a program does by just reading it. This skill will become more important as your quest continues to become a computer games developer.

The IF statement can be summarised like this:

IF something is true THEN do something about it

OK, let’s break this down. What do we mean by “something is true”. Well, in English I could say something like this:

IF I feel hungry THEN eat a biscuit

According to this statement I would only eat the biscuit if I feel hungry. Well, actually in real life I would eat the biscuit anyway, but don’t worry about that. It only confuses the issue.

So, how does this translate to computer speak? How about this:

10 LET A = 123
20 IF A = 124 THEN PRINT "A is equal to 124"

This program doesn’t actually output anything, as the PRINT statement is only executed IF A is equal to 124. We have actually given it the value 123 in line 10. If you want to prove this, then edit line 10 to change the value of A to 124, then run it again…

You can do any comparison, provided that the answer is either a YES (True) or NO (False). The computer will then only run the command if the answer is YES.

Here are some example comparisons:

>   Greater Than             (i.e. IF A > 1)
<   Less Than                (i.e. IF A < 100)
=   Equal To                 (i.e. IF A = 123)
<>  Not Equal To             (i.e. IF A <> 0)
>=  Greater Than or Equal To (i.e. IF A >= 10)
<=  Less Than or Equal To    (i.e. IF A <= 10000)

Note that you can also compare strings, so you can check IF A$ = “YES”. However strings and numbers are treated differently and you cannot compare apples with oranges. More on that later…

OK. We’ve got variables and decisions, now we’ll work on looping and I think we’ve got the basics cracked…