programming-for-dummies

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Looping Statements
Looping Statements
A looping statement repeats one or more commands for a fixed number of
times or until a certain Boolean condition becomes True. To create a loop
that repeats for a fixed number of times, use the FOR-NEXT loop, which
looks like this:
FOR variable = Start TO End
Command
NEXT
If you wanted the FOR-NEXT loop to run five times, you’d set the Start value
to 1 and the End value to 5, such as
FOR variable = 1 TO 5
Command
NEXT
Normally the FOR-NEXT loop counts by one, but you can use the STEP keyword
to make the FOR-NEXT loop count by any value, such as by three, as
shown in this example:
FOR variable = 1 TO 36 STEP 3
Command
NEXT
Rather than count up, the FOR-NEXT loop can also count down. In Visual
Basic, you can count down by using a negative number after the STEP keywords,
such as
FOR variable = 100 TO 1 STEP -1
Command
NEXT
In REALbasic, you can count down by replacing the TO keyword with the
DOWNTO keyword, such as
FOR variable = 100 DOWNTO 1
Command
NEXT
If you don’t know how many times you need to repeat commands, use a DO
loop. The two variations of a DO loop are DO-UNTIL and DO-WHILE (available
only in Visual Basic).