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My BASIC Quick Reference Guide

Abbreviation: F <SHIFT+O>

TYPE: Statement
FORMAT: FOR <variable> = <start> TO <limit> [ STEP <increment> ]

Action: This is a special BASIC statement that lets you easily use a variable as a counter. You must specify certain parameters: the floating-point variable name, its starting value, the limit of the count, and how much to add during each cycle.

Here is a simple BASIC program that counts from 1 to 10, PRINTing each number and ENDing when complete, and using no FOR statements:

100 L = 1
120 L = 1 + 1
130 IF L <= 10 THEN 110
140 END

Using the FOR statement, here is the same program:

100 FOR L = 1 TO 10
120 NEXT L
130 END

As you can see, the program is shorter and easier to understand using the FOR statement.

When the FOR statement is executed, several operations take place. The <start> value is placed in the <variable> being used in the counter. In the example above, a I is placed in L.

When the NEXT statement is reached, the <increment> value is added to the <variable>. If a STEP was not included, the <increment> is set to + 1. The first time the program above hits line 120, 1 is added to L, so the new value of L is 2.

Now the value in the <variable> is compared to the <limit>. If the <limit> has not been reached yet, the program G0es TO the line after the original FOR statement. In this case, the value of 2 in L is less than the limit of 10, so it GOes TO line 110.

Eventually, the value of <limit> is exceeded by the <variable>. At that time, the loop is concluded and the program continues with the line following the NEXT statement. In our example, the value of L reaches 11, which exceeds the limit of 10, and the program goes on with line 130.

When the value of <increment> is positive, the <variable> must exceed the <limit>, and when it is negative it must become less than the <limit>.

NOTE: A loop always executes at least once.

EXAMPLES of FOR...TO...STEP...Statement:

100 FOR L = 100 TO 0 STEP -1
100 FOR L = PI TO 6* {pi} STEP .01
100 FOR AA = 3 TO 3

Commodore Cheetah made by Allen Monks, started in the year 2000.