Atari 400

144 User's Handbook to the Atari 400/ 800 Computers
ON
The ON statement is used to branch program control. When
used with a
GOTO statement, the ON statement branches
program
control to one of several lines. An ON statement is also
used with GOSUB to branch a program to one of several
subroutines.
CONFIGURA TION
fGosuBj
ON X LGOTO}N[,LN] .. .
The argument
of ON is the control expression. When a GOSUB
statement is used, the program proceeds to a subroutine. When
a
GOTO statement is used, the program branches to a line
number.
The control expression determines to which line number the
program
will proceed. If the control expression equals 1, the
program branches
to the first line number after the GOTO or
GOSUB. If the control expression equals 2, the program
branches
to the second line number after GOTO or GOSUB, etc.
If the control expression does not equal an integer, it is rounded .
If the control expression eval uates to 0 or a number greater than
the number of choices of line numbers, the statement following
the ON statement is executed.
If the control expression is less than 0 or greater than 255, an
error results.
EXAMPLE
10 X = 2
20 ON X GOTO 30, 40 , 50
30 PRINT "FIRST" : END
40 PRINT "SECOND ": END
50 PRINT "THIRD": END
RUN
SECOND