Q28980: "NUL" Device Behaves Different in QB 4.x than 3.00 or GWBASIC

Article: Q28980
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 buglist4.50 | mspl13_basic
Last Modified: 24-JAN-1990

The NUL device in QuickBASIC Versions 4.00, 4.00b, and 4.50 behaves
differently than in previous versions of QuickBASIC (or in GW-BASIC
3.20).

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

When the program below is run (either inside the QB.EXE editor or from
an executable .EXE program), the (incorrect) output is as follows:

   third

When run inside the QuickBASIC Version 3.00 editor or compiled to an
EXE file with QB.EXE Version 3.00, or run in GW-BASIC Interpreter
Version 3.20, the (correct) output is as follows:

   first
   secondthird

With Version 4.00, the string BUFFER$ appears to be reinitialized with
each PRINT #1 statement.

If the device name is changed from NUL to anything else, for example
FOO, then QuickBASIC Versions 3.00 and 4.00 produce the same (correct)
output.

The following is a code example for this problem:

   open "nul" for random as #1
   field #1, 65 as buffer$
   print#1,"first"
   print#1,"second";
   print #1,"third"
   print buffer$

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