Qualcomm Embedded Software Developer interview questions

Normal C++ programming task : LinkedList, Data structure, Memory Management Conceptual questions: OS, RTOS

The first interviewer asked me questions about C and bit manipulation coding questions. The second interviewer was pretty nice. Also bit manipulation coding questions. The last guy was very unfriendly and seem like he didn't prepare any question. He asked me to write any code in C. So I wrote printf("hello world"). And then he started to ask me questions about designing printf and how it worked etc.. He refused to give me any hints. And he smirked at me when I had no clue. At the end of the interview, I asked if he could tell me what he could tell me the answer about a question he asked me before. He refused it by saying you can think about it on your way home.... ?? I got a nice offer from other company. I am so glad I don't have to work with this guy.