/X (Ignore Standard Include Paths)
Prevents the compiler from searching for include files in directories specified in the PATH and INCLUDE environment variables.
You can use this option with the /I (Additional Include Directories) (/I
To set this compiler option in the Visual Studio development environment
Open the project's Property Pages dialog box. For details, see Set C++ compiler and build properties in Visual Studio.
Click the C/C++ folder.
Click the Preprocessor property page.
Modify the Ignore Standard Include Path property.
To set this compiler option programmatically
In the following command,
/X tells the compiler to ignore locations specified by the PATH and INCLUDE environment variables, and
/I specifies the directory in which to look for include files:
CL /X /I \ALT\INCLUDE MAIN.C