title: Use external header files in MPLAB X IDE
body: <p>I have a folder with some .h and .c files and I want to use header files in my projects.</p>
  
  <p>I have included them in "Header Files" folder of my project using "Add Existing Item" but when i try to "#include" them compiler(mplabc18\v3.41) say "unable to locate file xyz.h"</p>
  
  <p>So, what should i do to use these files without copying them into the project folder?</p>