You can place either macros or inference rules in your TOOLS.INI file. NMAKE looks for the TOOLS.INI file first in the current directory and then in the directory indicated by the INIT environment variable.
If NMAKE finds a TOOLS.INI file, it looks for the following tag:
[nmake]
You can place macros and inference rules below this tag in the same format you would use in a description file.
If a macro or inference rule is defined in both the TOOLS.INI file and the description file, the definition in the description file takes precedence. Also, if you use the /R option, the TOOLS.INI file is ignored.