Where does Visual Studio look for C++ header files?

Visual Studio looks for headers in this order:

• In the current source directory.
• In the Additional Include Directories in the project properties (Project -> [project name] Properties, under C/C++ | General).
• In the Visual Studio C++ Include directories under Tools → Options → Projects and Solutions → VC++ Directories.
• In new versions of Visual Studio (2015+) the above option is deprecated and a list of default include directories is available at Project Properties → Configuration → VC++ Directories

In your case, add the directory that the header is to the project properties (Project Properties → Configuration → C/C++ → General → Additional Include Directories).

Actually, on my windows 10 with visual studio 2017 community, the path of the C++ header are:

1. C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.15.26726\include

2. C:\Program Files (x86)\Windows Kits\10\Include\10.0.17134.0\ucrt

The 1^st contains standard C++ headers such as <iostream>, <algorithm>. The 2^nd contains old C headers such as <stdio.h>, <string.h>. The version number can be different based on your software.

If the project came with a Visual Studio project file, then that should already be configured to find the headers for you. If not, you'll have to add the include file directory to the project settings by right-clicking the project and selecting Properties, clicking on "C/C++", and adding the directory containing the include files to the "Additional Include Directories" edit box.

It looks for files in the directory mentioned in options" cwd, you can include all sub directory under a path as shown below.

• it will create a single output file.
• it will compile all files together in the directory specified in cwd

project Structure:

moduelTest

-header_files
    - util.h
-source_files
    - util.c
    - main.c