#but it can wait...

Tron is tall as hell. He has got some complex code and I think he continuously built it as different threats appeared. Learning security program, it makes sense. Dude won't stop growing, it's just gradual enough no one notices. At first.

Clu is also tall for the same reason. He starts the same as Flynn, they're meant to look alike after all. But as the grid grows so does Clu, and eventually Flynn looks at him and goes:

"Did you get taller man?"

"Yes, a program's height is based on the complexity and length of their code. As the Grid changes, I must change with it."

"No way man! That's how that works???"

Also is why Rinzler is shorter. I am pretty sure Clu deleted or changes some things, and Rinzler's height changed accordingly :D

This is also why most rectified programs look so similar in build. Their code is all very similar, so they all look more alike than your average program.