This 125 page book is written for anyone that wants to be able to call C or C++ programs from IDL. Using very simple examples written in C and C++ the reader will be able to create and pass scalars, arrays, strings and structures back and forth from IDL to C. In addition a new chapter covers writing IDL object methods in C or C++. Chapters also cover the new keyword API available in IDL 5.6 and later, creating a dll project in Visual C++ 6, Visual Studio 2005 and debugging a DLM using Visual C++ or Emacs and gdb on Unix. Over 1000 lines of source code are provided on the accompanying disk with a makefile for all UNIX platforms, com file for VMS, Visual C++ 6.0 project for windows, Visual Studio 2005, and a Code Warrior 5 project for the Macintosh.