To create an application that uses the X Window System protocol, you should study the X Window System application programming interface. In addition, sample programs called XSAMP1, XSAMP2, and XSAMP3 (see Using sample X Window System programs) illustrate simple examples of programs that use the X Window System API. These programs are distributed with TCP/IP.

You should ensure that the first X header file your program includes is the XLIB.H header file. This file defines a number of preprocessor symbols, which enable your program to compile correctly. If your program uses the Xt Intrinsics, you should ensure that the INTRINSIC.H header file is the first X header file included in your program. This file contains a number of preprocessor symbols that allow your program to compile correctly. In addition, these header files include the MVS™ header files that remap the external names of the X Window System routines to the shorter names used by the X Window System that is supported by TCP/IP.