ACUCOBOL-GT includes a number of definition files. These files make it easier to use some of ACUCOBOL-GT's special features, such as graphical controls, color configuration, and Windows HELP. Many of the definition files contain predefined data structures for use with ACUCOBOL-GT runtime routines. You can include these structures easily in your program by COPYing the definition file into your program. All of the definition files have the three-character ".def" extension in their name. Most reside in the "sample/def" subdirectory of your ACUCOBOL-GT directory. How and when to use these files is documented with the feature or function that the file supports (such as with a runtime library routine or in the Special Names reference documentation).