Not quite a interview question, but in a competition (I had build a compiler) the jury (they all told me they had all studied informatics) asked me what a compiler is... Not in a "lets try to catch him off manner" but rather in a "i am too stupid for this world manner" he asked me what a compiler was... And it got even worse: my compiler is based on linuxes utils (nasm+ld) the guy didnt know about linux. Assembler was much too much for him and when my compiler threw an error (I wanted to show them the error system) he told me I shouldnt present unfinished projects... Atleastthe other two were really nice and i still got 2nd place (behind a person who prorammed an Nxt thingy)