Disney Villains

The Master Control Program (MCP), voiced by David Warner, is the primary antagonist of the original Tron movie, filmed in 1982. The MCP is the artificial intelligence used by ENCOM to run its computer network, as such it ruled the world inside ENCOM's mainframe. Inside the mainframe, the MCP grew by stealing data from other systems and forcing programs to align with itself. Programs that refused were enslaved and forced to the game grid to compete against MCP's henchmen.

Outside the mainframe, Kevin Flynn tries to hack in to ENCOM's mainframe in order to gather evidence against CEO Ed Dillinger (also played by David Warner). While doing so the MCP uses ENCOM's dematerialization gun to digitize Flynn and force him to play the games until he dies doing so.

In the system Flynn allies himself with Tron, a security program, and together they escape the game grid. They work together with the common goal of destroying the MCP and eventually succeed in derezzing the MCP.
Many of the MCP's communications with Ed Dillinger and Sark (MCP's henchman inside the computer world) end with the phrase "End of line." In the sequel, Tron: Legacy, Zuse (aka Castor) operates the End of Line Club, a tribute to the MCP of the original film.