Program Pak was Tandy/Radio Shack's name for its format of software cartridges designed for the CoCo's expansion/cartridge slot. Each Program Pak's contact pins had a distinctive spring-loaded protective hard plastic sleeve which was pushed back into the cartridge when the cartridge was inserted into the CoCo, and which sprag back to its protective covering position when the cartridge was removed.
By far, most Radio Shack branded software titles were released on Program Paks. (Third party developers usually released their titles on disk and/or tape). While cartridges had long been associated with video games, thanks to consoles such as the Atari 2600 and similar competitors, and while most Radio Shack CoCo video games were also on Program Paks, other, non-gaming software was also available on the cartridges, such as the Color SCRIPSIT and Color SCRIPSIT II word processors and others.