A major goal of the PI-API is to make user-written applications portable. On every installation supporting PI-API, there is a set of include files, one or more of which will be required to properly compile user-written applications.
For C programs, the piapix.h file provides access to all of the function prototypes and necessary defines to compile against the PI-API. This header file includes the extended PIAPI routines. This file also includes piapi.h for convenience. The location of this file may vary, depending on the platform. For portability, you should not specify the include directories and paths in your source file. Every compiler offers methods for specifying optional include file locations.
Compile options are platform-dependent, changing even between releases on the same platform.