From QB64 Wiki
ON...GOSUB is a control-flow statement that branches to a line or label in a list depending on a numerical expression.
- ON numerical-expression GOSUB lineornumber[,lineornumber][,...]
- The numerical-expression represents the line or label that it should branch to, 1 branches to the first line or label, 2 branches to the second, etc.
- In QB 4.5 the list can contain a maximum of 60 line numbers or labels, while QB64 has no limit.
- 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.
CLS a = 2 ON a GOSUB hello, hereweare, 143 PRINT "Also notice the RETURN statement that can be used with GOSUB!" END hello: PRINT "Hello, with a = 1 you get to see this!" END hereweare: PRINT "with a = 2 here we are...return to line after ON." RETURN 143 PRINT "Line 143, with a = 3 you get to see this!" END
with a = 2 here we are...return to line after ON. Also notice the RETURN statement that can be used with GOSUB!
- 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!