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56 lines
1.6 KiB
Markdown
56 lines
1.6 KiB
Markdown
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[ON...GOSUB](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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## Syntax
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> **ON** numericalExpression [GOSUB](GOSUB) labelOrNumber[,labelOrNumber][,...]
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## Description
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* 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](RETURN) returns to the next code statement after the [ON...GOSUB](ON...GOSUB) statement. [END](END) or [SYSTEM](SYSTEM) can be used to end program.
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* **Note:** [SELECT CASE](SELECT-CASE) provides a much more convenient way of doing this task.
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## QBasic
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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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## Example(s)
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```vb
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CLS
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a = 2
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*ON* a **GOSUB** hello, hereweare, 143
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PRINT "Also notice the RETURN statement that can be used with GOSUB!"
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END
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hello:
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PRINT "Hello, with a = 1 you get to see this!"
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END
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hereweare:
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PRINT "with a = 2 here we are...return to line after ON."
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RETURN
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143
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PRINT "Line 143, with a = 3 you get to see this!"
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END
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```
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```text
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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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```
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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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## See Also
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* [ON...GOTO](ON...GOTO)
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* [GOSUB](GOSUB), [GOTO](GOTO)
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* [SELECT CASE](SELECT-CASE), [RETURN](RETURN)
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