GDDM is a powerful and versatile "family" of IBM licensed programs that provides vital presentation services in IBM host data processing applications, particularly those services needed to present visual information. These services are comprised of a set of comprehensive and easy-to-use functions for showing data on IBM display terminals and other devices. GDDM will send the data to a wide range of devices besides displays, including printers, plotters, and host-attached personal computers. As well as output, GDDM accepts input, reading alphanumeric data from a keyboard, graphic data from a tablet or mouse, and image data from a scanner.
At the center of GDDM is a set of Base program routines used to create visual data (graphic, alphanumeric, and image) for display or print, and send it to one of an extensive number of supported output devices. These programs also can read device input and divide screens into independent windows GDDM Base provides a set of user interfaces in the form of a subroutine application programming interface (API), which is supported in a number of different programming languages, and several ready-made applications and functional utilities. The GDDM Presentation Graphics Facility (GDDM-PGF) provides a set of presentation-graphics API routines. These routines are a special purpose API which provides a simpler alternative to use of the Base API for drawing charts.
Application programmers can call the subroutines from the programs they write, enabling graphics, images, and alphanumeric text to be input to and output from application programs and GDDM utilities. The API subroutines facilitate easy and effective creation and display of data, while making it possible to avoid device and system dependencies. Many IBM and other software packages have already been written to take advantage of GDDM's capabilities. Some of these applications are discussed later in this information. You may find that you are already using one of these applications and were not aware that GDDM is the basis of the application's display and print capabilities. Indeed, you may find one that will suit your needs, saving you from writing an application program yourself.