In Tron (1982), what is the name of the program that controls the system?

The program controlling the computer system in Tron (1982) is the Master Control Program.

Usually abbreviated MCP, the Master Control Program is the film’s central artificial-intelligence antagonist. It has grown beyond its original purpose, takes control of other programs, and seeks to expand its authority over users and systems outside the computer world.

MCP traps Kevin Flynn inside the digital environment after Flynn is digitized by a laser. Within that world, programs appear in humanoid form and are forced into dangerous contests, including the film’s famous light-cycle battles. MCP’s presence gives Tron a conflict between individual programs and centralized computational control.

CLU is a separate program created by Flynn, TRON is a security program associated with Alan Bradley, and Sark is a human-shaped program serving MCP. Tron was directed by Steven Lisberger and released by Walt Disney Productions in 1982. Its computer-generated imagery and electronic aesthetic helped make it a landmark in science-fiction cinema.