[[ON...GOSUB]] is a control-flow statement that branches to a line or label in a list depending on a numerical expression.


{{PageSyntax}}
: '''ON''' {{Parameter|numericalExpression}} [[GOSUB]] {{Parameter|labelOrNumber}}[,{{Parameter|labelOrNumber}}][,...]


{{PageDescription}}
* {{Parameter|numericalExpression}} represents the ''line'' or ''label'' that the program should branch to: 1 branches to the first line or label in the list, 2 branches to the second, etc.
* The procedure must be used after the number value is determined or in a loop to monitor current user events.
* [[RETURN]] returns to the next code statement after the [[ON...GOSUB]] statement. [[END]] or [[SYSTEM]] can be used to end program.
* '''Note:''' [[SELECT CASE]] provides a much more convenient way of doing this task.


==QBasic/QuickBASIC==
* In QuickBASIC 4.5 the list could contain a maximum of 60 line numbers or labels, while '''QB64''' has no limit.


{{PageExamples}}
''Example:''
{{CodeStart}} '' ''
{{Cl|CLS}}
a = 2
''ON'' a '''GOSUB''' hello, hereweare, 143
{{Cl|PRINT}} "Also notice the RETURN statement that can be used with GOSUB!"
{{Cl|END}}

hello:
{{Cl|PRINT}} "Hello, with a = 1 you get to see this!"
{{Cl|END}}

hereweare:
{{Cl|PRINT}} "with a = 2 here we are...return to line after ON."
{{Cl|RETURN}}

143
{{Cl|PRINT}} "Line 143, with a = 3 you get to see this!"
{{Cl|END}} '' ''
{{CodeEnd}}
{{OutputStart}}
with a = 2 here we are...return to line after ON.
Also notice the RETURN statement that can be used with GOSUB!
{{OutputEnd}}

:''Explanation:'' Since ''a'' equals to 2 it goes to the second item in the list (''hereweare'') and branches the program to there. Try changing 'a' to 1 or 3.


{{PageSeeAlso}}
* [[ON...GOTO]]
* [[GOSUB]], [[GOTO]] 
* [[SELECT CASE]], [[RETURN]]


{{PageNavigation}}
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