Windows NT reads environment variables from AUTOEXEC.BAT at boot time

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Environment variables may be used to set compiler, assembler, and linker options. Settings made in this way will override settings made in the Visual Workbench and in makefiles. For example, the following setting will cause the compiler to pack structures on 1-byte boundaries, and this can cause problems when creating applications for Windows NT using Visual C++ 32-bit edition:

   SET CL=-Zp1
				

The following environment variables may affect development tools:

   CL       : C/C++ compilers
   ML       : MASM
   FL32, FL : FORTRAN compilers
   LINK     : Link
				

Environment variables set in AUTOEXEC.BAT can only be seen in a console session. To see the current environment variable settings, run a console session and enter the following command at a prompt: The resulting list may include variable settings that do not show up when checking the system settings in the Control Panel. These variables are probably being set in the AUTOEXEC.BAT file.

To prevent problems related to setting of unwanted environment variables in Windows NT, but to still allow them to be set when booting MS-DOS on a dual- boot machine, use a secondary batch file. For example, place all of the SET commands in the AUTOEXEC.BAT file in a file called DOSVARS.BAT. Save this file in the root directory of your boot drive (the same directory as AUTOEXEC.BAT). Add a line to execute this batch file to the end of AUTOEXEC.BAT (add it as the last line):

   DOSVARS
				

This will execute the batch file to set the variables and not return to the AUTOEXEC.BAT processing. You can also use the following

   CALL DOSVARS
				

at any point in the AUTOEXEC.BAT file so that processing of AUTOEXEC.BAT continues after the settings are made. Because Windows NT does not process nested batch files when reading AUTOEXEC.BAT, the variables will be set for DOS but not for Windows NT.