During the mainframe era, IBM made a wide variety of programs available to its customers. Programs were offered in two broad categories. The first category of programs were IBM developed and supported. These were termed Type I (Programming systems) and Type II (Application Programs). These programs were subjected to formal testing and were maintained by IBM.


The second category of available programs were termed Type III and Type IV programs. Type III (IBM Contributed Programs) and Type IV (Customer Contributed Programs) were programs of general interest contributed to the Program Information Department (PID) for distribution. These programs and their documents were distributed in the author's original form and were not subjected to any formal testing.


These libraries were maintained by the IBM Program Information Department, headquartered in Hawthorne, New York, with its distribution center in Mechanicsburg, Pennsylvania, which published separate catalogs for each compatible family of IBM Processors.^[1]


Originally, these programs were not individually priced, but were provided at no cost as part of IBM’s service. In 1969, IBM “unbundled,” separately pricing hardware, software, and services. The Type-III library was eventually replaced by several different product designations. Programs contributed by customers were known as "Installed User Programs" (IUPs) and those developed by IBM employees as "Field Developed Programs" (FDPs). The "field developed" moniker was something of a misnomer, as quite a few FDPs were written by employees in the IBM programming groups rather than by field personnel.

Some of the many Type-III programs offered by IBM include: