Apple IIe - Page 71

Applesoft BASIC Programming 71
the index variable A would be incremented by 2 every time the
NEXT statement was executed.
Nested Loops
One loop can be placed inside another loop. The innermost
loop is known as a nested loop . The following program contains
a nested
loop .
50 DIM R (2,3)
100 DAT A 10, 20, 30, 40, 50, 60
200 FOR I = 1 TO 2
300 FOR J = 1 TO 3
400 READ R (l,J)
450 PRINT R (l, J)
500 N. EXT J
600 NEXT I
Our preceding example is used to read data into the numeric
array R.
One error that you should take care to avoid when using nested
loops
is to end an outer loop before an inner loop is ended.
Conditional Statements
One of the most important features of a computer is its ability to
make a decision. BASIC uses the IF, THEN statement to take
advantage
of the computer's decision making ability . The IF,
THEN statement takes the following form:
IF expression THEN statement or line number
The IF statement sets up a question or a condition . If the answer
to that question is true , the statement or line number following
THEN is executed. If the answer is false, all instructions following
THEN are ignored, and program execution will resume with the
next line number in the program.
In
the following example, if 1 is input for X, the Y is set equal to 1.
Otherwise, Y's value remains 0.