Q21963: ENVIRON Statement Produces "Out of Memory" Error Message

Article: Q21963
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 | b_basiccom | mspl13_basic
Last Modified: 29-APR-1990

Most forms of the ENVIRON statement produce the run-time error message
"Out of memory" (on DOS Versions 2.x through 3.30). The following
example produces the "Out of memory" error message:

   ENVIRON "PATH=C:\COBOL"

The following example usually works correctly, however, the ENVIRON
statement is not very practical in QuickBASIC:

   ENVIRON "PATH=;"

Expanding the environment table cannot be done in a QuickBASIC program
because the size of the environment table is limited to its size
rounded up to the nearest multiple of 16 bytes, when QuickBASIC or a
QuickBASIC program is initiated.

QuickBASIC does not modify the actual DOS environment table; it only
modifies a local copy.

You can work around this problem by doing the following:

1. SET a large string in the MS-DOS environment table before running
   QB.EXE or a compiled program, as in the following example:

   SET JUNK=123456789012345678901234567890

2. Use the following ENVIRON statements in your program to set the
   large string equal to a null string, then you can allocate strings
   whose length totals up to the size that was deallocated:

   PRINT ENVIRON$("JUNK")  ' DOS environment variables MUST be
                           ' uppercase.

ENVIRON "JUNK=;"           ' This deallocates environment table
                           ' space.

PRINT ENVIRON$("JUNK")     ' This confirms deallocation; prints
                           ' nothing.

ENVIRON "TEST=C:\COBOL"    ' This sets up new environment string.

PRINT ENVIRON$("TEST")     ' This displays the new environment
                           ' string.

   Note that the MS-DOS environment variable names must be uppercase.

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