reverse engineering c programs

Question

every c program is converted to machine code, if this binary is distributed. Since the instruction set of a computer is well known, is it possible to get back the C original

Answer 1

Working on tools that do this is a research activity. That is, it is possible to get something in the easy cases (you won't recover local variables names unless debug symbols are present, for instance). It's nearly impossible in practice for large programs or if the programmer had decided to make it difficult.