Tron (1982)

When talented computer engineer Kevin Flynn (Jeff Bridges) finds out that Ed Dillinger (David Warner), an executive at his company, has been stealing his work, he tries to hack into the system. However, Flynn is transported into the digital world, where he has to face off against Dillinger's computerized likeness, Sark, and the imposing Master Control Program. Aided by Tron (Bruce Boxleitner) and Yori (Cindy Morgan), Flynn becomes a freedom fighter for the oppressed programs of the grid.