At least for the people who send me mail about a new language that they're designing, the general advice is: do it to learn about how to write a compiler
Dennis RitchieUNIX is simple and coherent, but it takes a genius (or at any rate, a programmer) to understand and appreciate its simplicity.
Dennis RitchieMy work was fairly theoretical. It was in recursive function theory. And in particular, hierarchies of functions in terms of computational complexity. I got involved in real computers and programming mainly by being - well, I was interested even as I came to graduate school.
Dennis Ritchie