Commodore Plus 4 - Page 84

LOOP in computerese. While you might want to do this, usually you
want to repeat only a certain number of times, or until something hap
pens That is why the FOR/NEXT and DO/LOOP statements are avail
able in BASIC
GOTO can also be used in direct mode. GOTO line # will start the
program at the line you specify, while keeping the variables the same
(instead of clearing them as RUN does).
Statement Name FOR NEXT
Format FOR variable = start value TO end value
some BASIC statements
NEXT variable
The FOR'NEXT statements let you create a loop that will repeat a
certain number of times The program statements between the FOR
statemenl and the matching NEXT statement are repeated in the loop
The variable in the FOR statement acts as a counter It is initially set at
the start value you supply. Then, the program lines after the FOR are
executed, until the computer gets to the matching NEXT statement.
The NEXT tells your Plus/4 to add one to the counter. If the counter is
less than or equal to the end value, ihe computer returns to the pro
gram line after the FOR statement. Otherwise, your Plus/4 continues
with the first statemenl after the NEXT
Example using a FOR'NEXT loop
10 PRINT."COUNTUP..."
20 FOR J - 1 TO 10
30 PRINT "WE HAVE";J
40 NEXTJ
50 PRINT "WE COUNTED UP TO";J
One more thing about FOR'NEXT you can also specify a STEP value in
the FOR statement. Instead of adding 1 to the counter variable, your
Plus/4 adds your STEP value. If you use a STEP of 5 with the statement
FOR M - 10 TO 30, for example, the counter would count 10, 15, 20,
25, 30 after each loop The STEP command even lets you count back
wards (by using a negative STEP value).
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