Apple IIe - Page 73

Applesoft BASIC Programming 73
In our preceding example, if the value input for A has a zero
value, then
the program will branch to line 900 where the
operator will be prompted whether he has finished entering
data. In line 910, the program will set up a condition where if the
input was 'N', the program will branch to line 100. If the entry was
not equal to 'N', the program will continue to line 999 where it
will end. ~
Note in line 910 that a GOTO statement is not used to precede
the line number being branched to. When a line number is
indicated following a THEN statement, the computer does not
require the presence of GOTO, which is " assumed.
ON, GOTO Statement
The ON, GOTO statement is a combination of a conditional
statement and a branching statement. The use of the ON, GOTO
statement is illustrated in the following program.
10 INPUT A
20
ON A GOTO 40, 50
30
GOTO 99
40 PRINT
"A= 1": GOTO 99
50 PRINT
"A= 2"
99 END
If the variable or expression following ON evaluates to 1,
program
control branches to the first line number specified after
GOTO; if 2, to the second; if 3, to the third, etc.
If the variable or expression evaluates to a number greater than
the number of line numbers following GOTO, program control
will branch to the statement immediately following the ON,
GOTO statement. This is also the case if the variable or
expression following ON evaluates to zero.
Subroutines & GOSUB Statements
Many times you will find that the same set of program instructions
are used
more than once in a program. Re-entering these
instructions
throughout the program can be very time con-