The story of Tron was that the MCP (Master Control Program, a super computer) had been allowed to get too big too control and in an effort to stop a disgruntled programmer (Jeff Bridges) from hacking into its secrets the MCP transformed him into a programme and absorbed him into itself. Tron was an anti virus programme designed to police the MCP but had instead been captured by the MCP and with the help of Bridges, Tron finally overcame the MCP which allowed Bridges to escape back into the real world.
There were two Tron games available for the Atari 2600 and the object of the game was to use elevators that moved up and down the screen to attempt to reach various objects that floated around the screen. This was not as easy as it sounded for you had to avoid tanks and Recognisers (security ships that looked like goal posts) that pursued you across the levels. There was only one screen which consisted of several floors and two sets of elevators and the game generally suffered from a chronic lack of things to do. As a result the game became monotonous very quickly for completing a level brought nothing different, merely an increase in difficulty.