The Master Control Program (MCP), voiced by David Warner, is the main villain of the Disney movie Tron. It is an artificial intelligence mainframe computer created by Ed Dilinger (also played by Warner) that ruled over the computer world. During the rule of the MCP, many programs were enslaved and forced to play games against its henchmen, Sark.
The MCP began life as a chess program. Ed Dillinger rewrote the program to administrate the ENCOM computer network (in effect an AI Superuser). However, the MCP had the capacity to learn and grew beyond the confines of its original programming. It began to steal data from other systems, and took control of several companies and institutions. The chess program Dillinger reprogrammed may have been one of the games he stole from Kevin Flynn. If true, this means Flynn wrote the MCP's AI. It would also make sense considering Flynn's poor appraisal of Dillinger's programming skills.
It is also a villain in Kingdom Hearts II, in the Tron-based world, Space Paranoids. It wants to kill Tron for interfering with its reign, and utilizes the Heartless to try and do so, even to the point of spawning virtual Heartless into the "real world" (Radiant Garden). However, even after, enhancing Sark to giant-size and fighting Tron, Sora and company directly, both he and Sark are destroyed.
Parodies
In the South Park episodes "Jewbilee" and "Super Best Friends", Moses took the form of the Master Control Program.