They asked me this question — what’s the difference between mutex and semaphore during an interview

It seems hard for my friend who is a self-taught developer.

Beginning

“Last week they asked me what is multi-threading and if have I ever done anything with that, I answered the question”. my friend said.

“Okay sounds good, hope you will pass it”. I told him.

“But then he asked me how to make sure resources safely be accessed in multi-threading situations”. he said.

“You should know lock right?” I told him.

“Yes I answered him lock but then he asked what is semaphore and what is the difference I have no idea what is semaphore so I told the interviewer I don’t know could you tell me what is that ?”. he said.

“then did he tell you the answer?” I asked.

“Yes, he said semaphore is a signal mechanism which is used for thread synchronization; and the purpose of a mutex is to protect resource access from other threads while only allowing one thread to use it,” he said.

“So you got it?” I asked.

“No…can you explain to me how it works under the hood without too many CS terms?” he asked.

Well, sure let me try.

Mutex

Okay, let’s forget about all these words signal, thread synchronization, and resource access.