During the arena sequence in Tron Legacy we see Sam take a grazing hit from a disk and bleed a few drops of blood, thus identifying him as a User.

From a plot and drama point of view this is very important but it appears to break the rules of the virtual world. Programs don't bleed, Quorra doesn't bleed, but Sam does. If he is a simulation within a virtual world how can he bleed? Or, more importantly, why is Sam simulated as having blood when programs do not?

Interesting points: in the original Tron movie Kevin Flynn seemed to absorb the energy of a program when it 'died' and was able to change colour, all of which indicate that he could interact with the world in ways different than other programs.

  • 1
    Shoddy coding: There's quite some memory leak, maybe the "hit" caused a buffer overrun and/or lost pointers. ;)
    – Mario
    Commented Jan 4, 2013 at 12:04

1 Answer 1


TL;DR : Sam bleeds because it's how his body would react when his skin is cut, so the simulation of his digitized body reacts the same way. Programs don't bleed because they are made of pure code, not a simulation of a physical body.

The presence of Sam in the virtual world is not the same as in other virtual worlds. He is not "Jacked-In" like in the Matrix, he is completely Digitized, all his molecules are transformed into code.

Flynn’s digitisation

Thus, if it's not real Sam that controls his simulation of himself from outside, it's a full and complete simulation of Sam that run, including his brain, all organs and of course, his blood.

If you ask how a 80's computer could run a full and complete simulation of a human being, well, it's just a movie! But the Grid seems to have done some simplifications, of adaptations to how it works. Users sometime react like a normal programs (the need of a disk, circuitry in the original Tron, etc.), but sometimes like humans (blood among others). It's like the simulation of a user works like a human locally, but like a program globally. The separation between those is more an artistic decision than a rationalized deductions.

As for programs, they don't bleed because nothing in their code says they need to bleed; they are built out of pure code. In Tron Legacy, when a program is hurt, the wounded part shatters into small cubes, a representation of the bits their code is built out of, literally their building blocks:

A "program getting "derezzed"

  • 3
    "shatter into small cubes" - Tron is Minecraft. Commented Jan 11, 2013 at 15:47

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