KnowledgeBase Archive

An Archive of Early Microsoft KnowledgeBase Articles

View on GitHub

Q38279: Long-Integer Array May Give Zero Unless Compiled /d (Debug)

Article: Q38279
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | B_BasicCom buglist4.00 buglist4.00b fixlist4.50 | mspl13_basic
Last Modified: 13-MAR-1990

Code Example 1 below shows a case where you must compile a QuickBASIC
Version 4.00 or 4.00b program that uses LONG-integer arrays with the
/d (debug) option, or else restructure the program as shown in Example
2. Otherwise, the result of a division with a LONG-integer array may
incorrectly result in zero.

Microsoft has confirmed this to be a problem in QuickBASIC Versions
4.00 and 4.00b, and in Microsoft BASIC Compiler Versions 6.00 and
6.00b for MS-DOS and MS OS/2 (buglist6.00, buglist6.00b). This problem
was corrected in QuickBASIC Version 4.50 and in Microsoft BASIC
Professional Development System (PDS) Version 7.00 for MS-DOS and MS
OS/2 (fixlist7.00).

When Code Example 1 below is compiled with BC.EXE in QuickBASIC
Version 4.00 or 4.00b, (in Microsoft BASIC Compiler Versions 6.00 and
6.00b for MS-DOS and OS/2, the debug (/d) option is required). If you
compile without using the /d option, the code produces the following
printout:

   20000  0  0  0
   20000  0  0  0
   20000  0  0  0

Code Example 1 displays the following correct results when executed
within the QB.EXE editor:

   20000  20000  0  0
   20000  20000  20000  0
   20000  20000  20000  20000

If you use a temporary variable to hold the value of Ddiv(ival) and
then divide by the temporary variable, the correct results are
generated (see Example 2).

[Note that QuickBASIC versions earlier than 4.00 and BASIC compiler
versions earlier than 6.00 do not support long integers.]

The following are code examples:

Example 1
---------

' Requires BC.EXE debug (/d) option in Versions 4.00 and 4.00b.
' OK in BC.EXE Version 4.50 with or without /d (debug) option.
DEFINT I, L: DEFLNG N: DEFDBL D
DIM NVal(3), NNum(3), Ddiv(5)
Ddiv(2) = 5
Ival = 2
FOR i = 0 TO 2
  NNum(i) = 100000
  NVal(i) = NNum(i) / Ddiv(Ival)
  PRINT NVal(i); NVal(0); NVal(1); NVal(2)
NEXT

Example 2
---------

' This works with or without /d (debug) option in Versions 4.00,
' 4.00b, and 4.50.
DEFINT I, L: DEFLNG N: DEFDBL D
DIM NVal(3), NNum(3), Ddiv(5)
Ddiv(2) = 5
Ival = 2
FOR i = 0 TO 2
  NNum(i) = 100000
  DTemp = Ddiv(Ival)
  NVal(i) = NNum(i) / DTemp
  PRINT NVal(i); NVal(0); NVal(1); NVal(2)
NEXT

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.