# Specifying Include Files

The Intel® C++ Compiler searches the default system areas for include files and items specified by the I compiler option. The compiler searches directories for include files in the following order:

1. Directories specified by the I option
2. Directories specified in the environment variables
3. Default include directories

Use the X (Windows*) or -nostdinc (Linux*)option to remove the default directories from the include file search path.

For example, to direct the compiler to search the path /alt/include instead of the default path, do the following:

This content is specific to C++; it does not apply to DPC++.

    // Linux and macOS*
    icpx -X -I/alt/include prog1.cpp

    // Windows
    icx /X /I\alt\include prog1.cpp

This content is specific to DPC++.

    // Linux and macOS*
    dpcpp -nostdinc -I/alt/include prog1.cpp

    // Windows
    dpcpp /X /I\alt\include prog1.cpp

Parent topic: Using the Command Line

## See Also

I compiler option
X compiler option
Supported Environment Variables