Bronze Edition Guide - True BASIC

48 BRONZE Edition Guide
The FOR-NEXT loop is a structure in True BASIC, or a kind of framework that organizes
other statements. The variable i in this program is called the index variable; it acquires
a new value each time the loop runs.
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x The same index variable must appear in both the FOR statement and the
NEXT statement.
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The statement(s) between the FOR and the NEXT statements are carried out (or executed)
as many times as the loop is repeated. In this book, the statements inside the loop (in this
case, the PRINT statement) are indented more than the FOR and NEXT statements. This
is a matter of style; it’s not required in True BASIC, but it makes the program much easier
to read.
The loop alters the straight-line flow of control by repeating a group of statements. Such
structures let you take advantage of the great power of computers.
Step Size in a Loop
The NEXT statement above added 1 to the index variable each time through the loop. You
can make the NEXT statement add something other than 1 by putting your own step size
in the FOR statement. For example, if you want a table of square roots in increments of
one-tenth, you can use .1 as the step size.
Open the demo program SQROOT from your True BASIC BRONZE Edition disk:
! Square roots.
!
PRINT “Number”, “Square Root” ! Print labels
PRINT
! Leave blank line
FOR number = 0 to 1 step .1 ! From 0 to 1 in small steps
PRINT number, Sqr(number) ! Print number & square root
NEXT number
END
and run it:
Number
Square Root
0 0
.1 .31622777
.2 .4472136
.3 .547722256
.4 .63245553