Microsoft KB Archive/35969

Knowledge Base

Do Not Mix Arrayname AS Type and % Type Suffix in DIM/COMMON

Article ID: 35969

Article Last Modified on 11/21/2006

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APPLIES TO

• Microsoft QuickBASIC 1.0b
• Microsoft QuickBasic 4.0
• Microsoft QuickBASIC 4.0b
• Microsoft QuickBasic 4.5 for MS-DOS
• Microsoft BASIC Compiler 6.0
• Microsoft BASIC Compiler 6.0b

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This article was previously published under Q35969

SYMPTOMS

Do not mix the use of "AS Type" declaration syntax with explicit type declaration suffixes (%, &, !, #, and $) with a given array name that occurs in both DIM and COMMON statements. Programs should be run in the QuickBasic QB.EXE editor to catch such a mismatch error.

If you compile Example Program 1 (below) with the BC /D (debug) option, then the .EXE file will produce an error at run time. If you do not compile with BC /D (debug) option, then the mismatched DIM/COMMON declaration will not be detected, and the resulting .EXE file will hang the machine, requiring a cold boot.

This article applies to Microsoft QuickBasic 4.00, 4.00b, and 4.50 and to Microsoft Basic Compiler Versions 6.00 and 6.00b (buglist6.00, buglist6.00b) for MS-DOS and MS OS/2. This problem was corrected in Microsoft Basic PDS Version 7.00 (fixlist7.00) for MS-DOS and MS OS/2.

MORE INFORMATION

For the example program below, Basic PDS 7.00 produces the following message for this error:

COMMON SHARED /x/ x() AS INTEGER ' AS INTEGER used for type declare.
^ AS clause required on first declaration

In Example Program 1, the array x% is treated as different from array x. Because the AS clause takes precedence over the "%" type suffix, BC.EXE declares the array x in COMMON as a dynamic array, replacing the static array x% that was dimensioned with the DIM statement. Thus, when the final .EXE is run, array bounds are exceeded, and the machine hangs (without BC /D) or gives a run-time error (with BC /D).

When run in the QB.EXE editor, the following program gives the error "AS Clause required in first declaration" due to illegal mixing of type declaration methods:

' Example Program 1
DIM x%(100)    ' % used for type declaration
COMMON SHARED /x/ x() AS INTEGER   ' AS INTEGER used for type declare.
FOR i% = 0 TO 99
  PRINT "i% = "; i%
  x%(i%) = 1
NEXT i%
                

The following program shows a correct method for type declaration:

' Example Program 2
DIM x%(100)
COMMON SHARED /x/ x%()
FOR i% = 0 TO 99
  PRINT "i% = "; i%
  x%(i%) = 1
NEXT i%
                

The following program shows another correct method for type declaration:

' Example Program 3
DIM x(100) AS INTEGER
COMMON SHARED /x/ x() AS INTEGER
FOR i% = 0 TO 99
  PRINT "i% = "; i%
  x(i%) = 1
NEXT i%
                

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

Keywords: KB35969

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