Apple IIe - Page 128

128 Apple lie Users Handbook
ON
• Applesoft
o Integer
The ON statement is used in conjunction with GOTO and
I
GOSUB. The statements are used to branch program control to
one of several program lines depending on the value appearing
after ON .
Configuration
ON exp GOTO line [,line ... ]
ON exp GOSUB line [,line ... ]
exp can be any
numeric constant or numeric expression. line is
the line number the program is to branch to.
The value
of exp controls which line is to be branched to. For
instance,
if exp evaluates to 1, program control will branch to the
line number given in the first line .. lf exp evaluates to 2, program
control will branch to the second line , etc. ..
If the ON . .. GOSUB statement is being used, the line number
specified in line must be that of a subroutine. In other words, a
RETURN
statement eventually will have to be executed to return
program control.
If exp evaluates to zero or to a number greater than the number
of lines specified after GOTO or GOSUB, the program will
continue with the next executable statement.
Example
10 INPUT "ENTER A NUMBER BETWEEN 1AND4 ";I
20 ON I GOTO 60,80,100,120
30 PRINT
40 INPUT "PLEASE ENTER A NUMBER BETWEEN 1 AND 4 ";I
50 GOTO 20
60 PRINT "YOU ENTERED A ONE"
70 GOTO 130
program co ntinued on the next pa ge