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Q40631: QB.EXE 4.x Won’t Trace or Single Step through KEY Routine

Article: Q40631
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | buglist4.00 buglist4.00b buglist4.50 SR# S881220-50 ptm240 | mspl13_basic
Last Modified: 8-MAR-1989

When single stepping or tracing through a program, the QB.EXE Version
4.00, 4.00b, or 4.50 editor executes key-trapping or event-trapping
routines correctly, but fails to display the tracing through the
routine unless you place a breakpoint there.

Microsoft has confirmed this to be a problem in Versions 4.00 and
4.00b. We are researching this problem and will post new information
as it becomes available.

QuickBASIC Version 3.00 successfully displays the single stepping or
tracing through key-trapping or event-trapping routines.

This article applies to all forms of ON Event GOSUB, where the
Event can be COM(n), KEY(n), PEN, PLAY(q), STRIG(n), and TIMER(n).

To trace through a program in QuickBASIC Versions 4.x, choose the
Debug menu, toggle the Trace On option, and run the program. (In
QuickBASIC Version 3.00, insert the statement TRON as the first
statement of the program and run it.)

To Single Step through a program in QuickBASIC Versions 4.x, press F8
repeatedly. (In QuickBASIC Version 3.00, you need to choose DEBUG from
the Run menu, then press F8 repeatedly.)

When you single step or trace the program below in the QuickBASIC
Versions 4.00, 4.00b, and 4.50 editors, press F1 or F2 while the
program is waiting for INPUT activates the key-trapping routine. After
you press ENTER to terminate the INPUT, the editor executes the
key-trapping routine but does not display the single stepping or
tracing.

To work around this behavior, set a breakpoint at the label of the
key-handling routine to stop execution at the label. Then, the QB.EXE
editor correctly single steps or traces through the key routine. You
can press F5 to continue tracing or press F8 for single stepping.

The following is a code example:

ON KEY(1) GOSUB KeyRoutine1
ON KEY(2) GOSUB KeyRoutine2
KEY(1) ON
KEY(2) ON
WHILE 1
INPUT "Press F1 or F2 and then hit ENTER key", X$
WEND
END
KeyRoutine1: 'Must set a breakpoint here to single step
                   'or trace through this routine.
   PRINT "inside key routine 1"
   RETURN
KeyRoutine2: 'Must set a breakpoint here to single step
                   'or trace through this routine.
   PRINT "inside key routine 2"
   RETURN

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