"Tron Legacy" was the name of an uncompiled data code featured in the videogame TRON 2.0. It was intended as an update for the security program Tron, written by the Alan Bradley for the purpose of clearing the Game Grid of any unauthorized users. In the year 2003, Alan's son Jet - having been digitized and sent into the Game Grid by the program Ma3a - found the code on an old ENCOM EN-82 server and stored it inside Ma3a. Unfortunately, the addition of the Legacy Code not only increased her size dramatically but also made her unstable and driven to attack any nearby users.
The Legacy Code is also mentioned in the graphic novel TRON: The Ghost in the Machine. Following Jet's return to the Game Grid, his old friend Mercury claimed the code was present in Jet's identity disc and that he would need it to defeat the MCP. The assertion proved to be false and was later revealed to be part of a hallucination Jet was experiencing.