If you look at see what SunOS version the Grid is running, when Sam sits down at his dad's old workstation, it doesn't match up with the timeline.
A couple seconds later in the movie, the hero is disintegrated by a laser cannon behind his back, scanned and transfered to virtual reality environment where programs break apart when they hit hard things. Suspension of disbelief is a requirement.
OTOH, I am quite surprised Disney got to name its first Tron villain the same as Burroughs mainframe OS. It's worth noting MCP's sidekick name sounds a lot like MARC (the Menu Assisted Resource Control).
That bit always made me laugh. Tron leads you to believe that the exciting/magical part is the virtual world, while I always thought the laser was the real world changing invention.
The guy creates a compact, cheap, abundant and unlimited power source and a form of non-reactive propulsion and what does he do with it? He builds a suit!
The part I found unbelievable: in spite of the fact that Stark Industries is prepared to sell us everything we need to live in an Asimovian future, their stock price is tanking because Stark wants to stop building weapons.
I paused one of the trailers at 1080p and captured the workstation desktop and I've been using it as a desktop background - quite a few people have told me that I really need to clean my monitor...
END OF LINE