QB64-PE/internal/help/GOSUB.txt

[[GOSUB]] sends the program flow to a sub procedure identified by a line number or label.


{{PageSyntax}}
: GOSUB {{{Parameter|lineNumber}}|{{Parameter|label}}}


{{PageDescription}}
* Use [[RETURN]] in a sub procedure to return to the next line of code after the original [[GOSUB]] call. [[END]] or [[SYSTEM]] can also be used to end program.
<!-- needs clarification: * A procedure loop may be used to return automatically instead of using return. -->
* GOSUB and GOTO can be used '''within''' [[SUB]] or [[FUNCTION]] procedures, but cannot refer to a label located outside the procedure.


==QBasic/QuickBASIC==
* 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.


{{PageExamples}}
''Example:'' Simple usage of GOSUB
{{CodeStart}}
{{Cl|PRINT}} "1. It goes to the subroutine."
{{Cl|GOSUB}} subroutine
{{Cl|PRINT}} "3. And it returns."
{{Cl|END}}

subroutine:
{{Cl|PRINT}} "2. It is at the subroutine."
{{Cl|RETURN}}

{{CodeEnd}}
{{small|Code by Cyperium}}
{{OutputStart}}
1. It goes to the subroutine.
2. It is at the subroutine.
3. And it returns.
{{OutputEnd}}




''Example:'' What happens if two GOSUB executes then two RETURN's?
{{CodeStart}}
start: 
 
a = a + 1 
{{Cl|IF...THEN|IF}} a = 1 {{Cl|THEN}} {{Cl|GOSUB}} here: {{Cl|PRINT}} "It returned to IF a = 1": {{Cl|END}} 
{{Cl|IF...THEN|IF}} a = 2 {{Cl|THEN}} {{Cl|GOSUB}} there: {{Cl|PRINT}} "It returned to IF a = 2": {{Cl|RETURN}}
 


here: 
{{Cl|PRINT}} "It went here." 
{{Cl|GOTO}} start

there: 
{{Cl|PRINT}} "It went there." 
{{Cl|RETURN}} 
{{CodeEnd}}
{{small|Code by Cyperium}}
{{OutputStart}}
It went here.
It went there.
It returned to IF a = 2
It returned to IF a = 1
{{OutputEnd}}
''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.


{{PageSeeAlso}}
* [[ON...GOSUB]]
* [[ON...GOTO]], [[GOTO]]
* [[ON ERROR]], [[RESUME]]
* [[ON TIMER (n)]]
* [[Line number]]


{{PageNavigation}}
<