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55 lines
1.8 KiB
Plaintext
55 lines
1.8 KiB
Plaintext
[[ON...GOSUB]] is a control-flow statement that branches to a line or label in a list depending on a numerical expression.
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{{PageSyntax}}
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: '''ON''' {{Parameter|numericalExpression}} [[GOSUB]] {{Parameter|labelOrNumber}}[,{{Parameter|labelOrNumber}}][,...]
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{{PageDescription}}
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* {{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.
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* The procedure must be used after the number value is determined or in a loop to monitor current user events.
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* [[RETURN]] returns to the next code statement after the [[ON...GOSUB]] statement. [[END]] or [[SYSTEM]] can be used to end program.
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* '''Note:''' [[SELECT CASE]] provides a much more convenient way of doing this task.
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{{PageQBasic}}
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* In QuickBASIC 4.5 the list could contain a maximum of 60 line numbers or labels, while '''QB64''' has no limit.
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{{PageExamples}}
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''Example:''
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{{CodeStart}} '' ''
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{{Cl|CLS}}
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a = 2
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''ON'' a '''GOSUB''' hello, hereweare, 143
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{{Cl|PRINT}} "Also notice the RETURN statement that can be used with GOSUB!"
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{{Cl|END}}
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hello:
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{{Cl|PRINT}} "Hello, with a = 1 you get to see this!"
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{{Cl|END}}
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hereweare:
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{{Cl|PRINT}} "with a = 2 here we are...return to line after ON."
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{{Cl|RETURN}}
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143
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{{Cl|PRINT}} "Line 143, with a = 3 you get to see this!"
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{{Cl|END}} '' ''
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{{CodeEnd}}
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{{OutputStart}}
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with a = 2 here we are...return to line after ON.
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Also notice the RETURN statement that can be used with GOSUB!
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{{OutputEnd}}
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:''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.
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{{PageSeeAlso}}
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* [[ON...GOTO]]
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* [[GOSUB]], [[GOTO]]
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* [[SELECT CASE]], [[RETURN]]
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{{PageNavigation}}
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