A C compiler for Brainfuck
I want to share my friend's crazy project because it demonstrates how a simple Turing-machine-like programming language is actually equivalent to usual real-world computers.
I think we all know the theory that all Turing complete programming languages are equivalent in terms of their powers. If languages A and B are Turing complete, A can emulate B and vice versa. But that's not obvious at all. How can a simple programming model like Turing Machine can run "real" programs such as ones that run on a general-purpose PC? If it is possible in theory, it can be demonstrated.