Cheers, so my textbook explains these parts very poorly, so I would gladly take any advice! I am confused between the test-and-set instructions, which per my book is a very common CPU instruction set, and the use of semaphores for which my book says that: a flag implemented using this way, is a semaphore. Does that mean that semaphores are a part of these instructions or the opposite? Also, if a operating system does not support semaphores, can it support test-and-set instructions and if yes, can you reach mutual exclusion this way? Thanks!