How does casting work in C (memory)? Difference between big-endian vs. little-endian? How can you tell if the machine you are coding on is big-endian or little-endian? Union vs struct, how does union work in memory? How does struct padding work, where are the extra bytes stored in memory? (4 bytes aligned) Was asked to find the errors in some C code: returning stack pointer, allocating huge array on the stack, integer overflow Given a sorted array, check whether number exists (use binary search, let me use python) Given a string with numbers and letters, remove all the non-numbers from the string, and convert that string to an int in C Basic OS stuff: What is multithreading? What is a mutex, and why do you need it? What is deadlock? Do threads share the same stack?