ON...GOSUB Example from QB 4.50 Help Gives "Label Not Defined" (58609)

SUMMARY

The ON...GOSUB example from the QB Advisor online Help system in Microsoft QuickBasic Version 4.50 causes a "Label not defined" error when run without modification. This is not a documentation error, since the preface to the example states "the following program fragment...", thus implying that the code is incomplete.

The Microsoft Advisor online Help system for QBX.EXE (QuickBasic Extended) in Microsoft Basic Professional Development System (PDS) Version 7.00 for MS-DOS has a complete working example for ON...GOSUB.

MORE INFORMATION

ON...GOSUB Example from QB.EXE Version 4.50

The following example, taken from the ON...GOSUB example in the QuickBasic 4.50 online Help system, produces a "Label not defined" error on the ON...GOSUB statement:

'The following program fragment causes program control to branch to
'one of the four subroutines listed, depending on the value of Chval:

DO
    CLS
    PRINT "1) Display attendance at workshops."
    PRINT "2) Calculate total registration fees paid."
    PRINT "3) Print mailing list."
    PRINT "4) End program."
    PRINT : PRINT "What is your choice?"
    DO
       Ch$ = INKEY$
    LOOP WHILE Ch$ = ""
    Chval = VAL(Ch$)
    IF Chval > 0 AND Chval < 5 THEN
        ON Chval GOSUB Shop, Fees, Mailer, Progend
    END IF
LOOP
END

To use the above example, you must define the four GOSUB labels (Shop:, Fees:, Mailer:, and Progend:).

ON...GOSUB Example from QBX.EXE Version 7.00

The following similar example from the QBX.EXE online Help system runs without error:

'This example uses the ON...GOSUB statement to cause program control to
'branch to one of three subroutines, depending on the value of Chval.

CLS    'Clear screen.
Attend = 20
Fees = 5 * Attend
PRINT "1  Display attendance at workshops"
PRINT "2  Calculate total registration fees paid"
PRINT "3  End program"
PRINT : PRINT "What is your choice?"
Choice:
    DO
       ch$ = INKEY$
    LOOP WHILE ch$ = ""
    Chval = VAL(ch$)
    IF Chval > 0 AND Chval < 4 THEN
        ON Chval GOSUB Shop, Fees, Progend
    END IF
END
Shop:
    PRINT "ATTENDANCE IS", Attend
    RETURN Choice
Fees:
    PRINT "REGISTRATION FEES ARE $"; Fees
    RETURN Choice
Progend:
    END