That sounds to me as if the interviewer had said "write a program". It seems rather natural to ask "OK. What do you want the program to do? Shall I write a prog

That sounds to me as if the interviewer had said "write a program". It seems rather natural to ask "OK. What do you want the program to do? Shall I write a program that takes some input, and outputs it reversed? Would that do?", and they said "If that's what you think a program is, then sure." At that point, it's probably best to stop arguing, and code. They probably want to argue with you about your code, not their spec. But when I got the reply "Do you not know what a state machine is?", I think I might have thanked them for their time, and left. I would have been sorely tempted to come back with "Yes, a state machine is an abstraction, and you seem to want a concrete implementation, but you don't seem to want to fill in the details of your requirement. Is it a good use of our time together for me to complete your spec, so there's something for me to code up?" It sounds like they didn't want you; perhaps your face didn't fit. They say most interviews are decided in the first couple of minutes.