Microsoft KB Archive/42324

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Period in Name of NAMED COMMON Can Erase BLANK COMMON Values

Article ID: 42324

Article Last Modified on 11/21/2006

This article was previously published under Q42324


The following information applies to the QB.EXE editor in Microsoft QuickBasic Versions 4.00, 4.00b, and 4.50 and to QB.EXE in Microsoft Basic Compiler Versions 6.00 and 6.00b.

When CHAINing between two programs that contain COMMON blocks, the values are not passed under the following conditions:

  1. Both programs contain at least one blank and one named COMMON block.
  2. The program being CHAINed to contains an additional COMMON block with variables declared as a user-defined TYPE.
  3. The "Names" of the named COMMON blocks contain periods.

The COMMON values are passed correctly if the periods are removed from the names in the COMMON blocks, or if the additional COMMON block with a user-defined TYPE is removed.

This problem occurs only when running the programs from within the QB.EXE environment. It does not occur when the programs are run as compiled programs.


Microsoft has confirmed this to be a bug in QuickBasic Versions 4.00, 4.00b, and 4.50, and in QB.EXE in Microsoft Basic Compiler Versions 6.00 and 6.00b (buglist6.00, buglist6.00b). The problem was corrected in QBX.EXE in Microsoft Basic Professional Development System (PDS) Version 7.00 (fixlist7.00).

Code Example

If the following program is run inside the QuickBasic environment, the values in the blank COMMON block are not passed to PROGRAM #2. If the COMMON block name /named.block1/ is changed to /namedblock1/ or the COMMON block following the user-defined TYPE in PROGRAM #2 is removed, then the values are passed correctly, as follows:

COMMON SHARED a1%, a2&, a3!, a4#
COMMON SHARED /named.block1/ b1%, b2&, b3!, b4#

a1% = 1: a2& = 64000: a3! = 1.5: a4# = 64000.5
CHAIN "prog2.bas"

TYPE UserDefinedType
COMMON SHARED a1%, a2&, a3!, a4#
COMMON SHARED /named.block1/ b1%, b2&, b3!, b#
COMMON SHARED /namedblock2/ var1 AS UserDefinedType

PRINT a1%, a2&, a3!, a4#

To prevent this problem, and to follow a good general rule, use only a period in a name when accessing a field of a variable that is DIMensioned as a user-defined TYPE.

Additional query words: QuickBas BasicCom B_BasicCom buglist4.00 buglist4.00b buglist4.50

Keywords: KB42324