Commodore Plus 4 - Conditional statements

CONDITIONAL
OR
DECISION
MAKING
STATEMENTS
Conditional statements are used to make decisions. One of the most
powerful abilities of a computer is to make decisions based on what is
going on. One of the conditional statements available on Ihe Plus-4 is
known as IF'THEN statements, —
Statement Name: IF/THEN
Format: IF condition THEN do this (only if the condition is true)
Basically, the IF'THEN statement works like this.
IF (this statement is true) THEN (do this statement)
Actually, you have always known how conditional statements work
How many times have you heard this famous line9
IF you eat all your vegetables THEN you can have dessert That may
seem a bit trivial, but that is the gist of the IF;THEN statement.
If the condition in the IF statement is true, everything after the THEN
is executed.
EXAMPLE.
10 INPUT'WHAT'S THE TENTH LETTER OF THE ALPHABET"; AS"
20 IF AS^-J11 THEN PRINT "RIGHT": GOTO 100
30 INPUT "IS THIS AN A";X$
40IFXS = "A"THEN60
50 PRINT "WRONG, TRY AGAIN": GOTO 30
60 PRINT"TYPE AB"
70 GETKEYA$:IFA$ = "B"THEN PRINT "RIGHT"
100 PRINT "THAT'S ENOUGH OF THIS, ANYWAY"
In line 40, we just say THEN 60. This actually means THEN GOTO 60. j
but since the THEN GOTO combination is used so often, BASIC allows
you to leave off the GOTO. An optional step for the IF'THEN statement
is the ELSE clause, that directs your computer to a specific action if
the original IF condition was not met- An example showing the ELSE
clause would be: IF B > 5 THEN 40 ELSE GOTO 10. The BASIC Ency- -
clopedia explains the IF/THEN/ELSE statement more fully.
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