Module basic::__Chapter_2::FOR

FOR <variable>=x TO y [STEP z]

Where x, y, and z are expressions.

Purpose

Used with NEXT to repeat execution of statements while iterating over a sequence of numbers.

Remarks

If we wanted the numbers 1,3,5,7 we would write FOR I=1 TO 7 STEP 2. On the first iteration, 1 will be assigned to variable I. Statements execute until a NEXT statement. On subsequent iterations, the variable I gets 2 added to it. If the result exceeds 7 the loop breaks. Otherwise the statements get executed again.

The first iteration will evaluate x, then y, then z. Newer versions of BASIC evaluate z first.

The first iteration always executes even if starting past the end. Newer versions of BASIC may skip the first iteration.

Example 1

10 I=9
20 FOR I=1 TO 10 STEP I
30 PRINT "HELLO WORLD";i
40 NEXT I
RUN
HELLO WORLD 1
HELLO WORLD 10

Example 2

10 FOR X=1 TO 2
20 FOR Y=5 TO 6
30 PRINT x,y
40 NEXT Y,X
RUN
 1  5
 1  6
 2  5
 2  6