Q40154: QB.EXE "OUT OF MEMORY" after SHELL to DOS PRINT, MODE, ASSIGN

Article: Q40154
Product(s): See article
Version(s): 2.00 2.01 3.00 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | SR# S881220-74 B_BasicCom | mspl13_basic
Last Modified: 14-DEC-1989

The MS-DOS PRINT, MODE, and ASSIGN commands should not be run from the
QuickBASIC environment during a SHELL or from a SHELL statement in an
executable program. The MS-DOS PRINT, MODE, and ASSIGN commands remain
resident in memory after being invoked. Subsequent attempts to LOAD
another QuickBASIC program that is larger or adds more code to an
existing program result in the error message "OUT OF MEMORY." You must
exit QuickBASIC and reboot to eliminate this memory-fragmentation
problem.

When the MS-DOS PRINT, MODE, and ASSIGN commands are invoked, they are
loaded into memory above QuickBASIC and the program loaded in the
environment. This causes memory to become fragmented. Although there
may be more memory above the resident commands, QuickBASIC will not
recognize this memory.

A QuickBASIC program that SHELLs to an MS-DOS batch file containing
the PRINT, MODE, or ASSIGN command usually executes correctly.
However, if an attempt is made to unload the current program and load
in a program that is larger than the first, the "OUT OF MEMORY" error
message displays. If you exit QuickBASIC and then bring QuickBASIC up
again, any attempt to load a program into the environment also
generates the error message.

If any application invoked after this is larger than QuickBASIC, the
following error displays: "PROGRAM TOO LARGE TO FIT IN MEMORY." The
only way to alleviate this situation is to reboot the machine. Exiting
QuickBASIC and then running QB.EXE again does not eliminate the
problem.

This information applies to Microsoft QuickBASIC Versions 2.00, 2.01,
3.00, 4.00, 4.00b, and 4.50 for MS-DOS and to the QBX.EXE environment
of Microsoft BASIC PDS Version 7.00.

To work around this problem, invoke the MS-DOS PRINT, MODE, or ASSIGN
command before running QB.EXE. You should never SHELL to any
terminate-and-stay-resident (TSR) program (such as the MS-DOS PRINT,
MODE, or ASSIGN command).

The following code example demonstrates the memory-fragmentation
problem:

   cls
   print "start"
   shell "test.bat"
   print "done"
   end

The following is the batch file TEST.BAT:

   mode com1:300,N,8,1,bin
   mode lpt1:=com1:

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