Commodore PET User Manual page 149

ON ... GOSUB
The ON ... GOSUB statement provides conditional subroutine calls to one
of several subroutines in a program. depending on the current value of the
specified index.
Format:
ON index GOSUB linel.line2..... Iine n
where:
index is a constant. variable. or expression that must
be in the range 0<index::;.255.
Iinei is one or more line numbers specifying the
beginning lines of subroutines.
ON ... GOSUB has the same format as ON ... GOTO. and the statement is
evaluated in the same way (see ON ... GOTO).
For index=l. the subroutine beginning at linel is called. When that
subroutine is completed (a RETURN statement). the program continues with the
statement following the ON GOSUB. If index=2. the subroutine beginning
with line2 is called, etc. The ON GOSUB statement should be used only to cali
subroutines that retum control via RETURN statements to the statement following
the ON GOSUB.
ON GOSUB is normally executed in program mode. It may be executed in
immediate mode as long as there are corresponding line numbers in the current
stored program that may be branched to.
Example:
10 ON A GOSUB 100.200.300
ON ... GOTO
The ON ... GOTO statement provides conditional branching to one of
several points in a program. depending on the current value of the specified index.
Format:
ON index GOTO linel.line2..... Iine n
where:
736
index
Iinei
is a constant. variable. or expression that must
be in the range 0<index::;.255.
is one or more line numbers.