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56 lines
2 KiB
Text
56 lines
2 KiB
Text
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'''GOSUB''' sends the program to a sub program that uses a line number or label.
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{{PageSyntax}}
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:: GOSUB label
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* Label is any [[line number]] or line label designated with a colon after it. Don't use the colon in the call.
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* [[RETURN]] at the end of the procedure returns to the next code after the original call. [[END]] or [[SYSTEM]] can also be used to end program.
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* A procedure loop may be used to return automatically instead of using return.
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* GOSUB and GOTO can be used '''within''' [[SUB]] or [[FUNCTION]] procedures, but cannot refer to a label not in the procedure itself.
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* '''Note:''' Too many GOSUBs without a [[RETURN]] can eventually cause "Out of Stack Errors" in Qbasic as each GOSUB uses memory to store the location to return to. Each [[RETURN]] frees the memory of the GOSUB it returns to.
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{{PageExamples}}
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''Example:''
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{{CodeStart}}
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start:
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a = a + 1
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{{Cl|IF...THEN|IF}} a = 1 {{Cl|THEN}} {{Cl|GOSUB}} here: {{Cl|PRINT}} "It returned to IF a = 1": {{Cl|END}}
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{{Cl|IF...THEN|IF}} a = 2 {{Cl|THEN}} {{Cl|GOSUB}} there: {{Cl|PRINT}} "It returned to IF a = 2": {{Cl|RETURN}}
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here:
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{{Cl|PRINT}} "It went here."
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{{Cl|GOTO}} start
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there:
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{{Cl|PRINT}} "It went there."
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{{Cl|RETURN}}
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{{CodeEnd}}
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{{small|Code by Cyperium}}
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{{OutputStart}}
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It went here.
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It went there.
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It returned to IF a = 2
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It returned to IF a = 1
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{{OutputEnd}}
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''Explanation:'' When a = 1 it uses GOSUB to go to "here:", then it uses GOTO to go back to "start:". a is increased by one so when a = 2 it uses GOSUB to go to "there:", and uses RETURN to go the last GOSUB (which is on the IF a = 2 line), it then encounters another RETURN which makes it return to the first GOSUB call we used on the IF a = 1 line.
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''See also:''
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* [[ON...GOSUB]]
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* [[ON...GOTO]], [[GOTO]]
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* [[ON ERROR]], [[RESUME]] {{text|{Error handlers only)}}
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* [[ON TIMER (n)]]
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* [[Line number]] {{text|(removal program)}}
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{{PageNavigation}}
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