what are the differences among mutex, condition variables, and semaphore?
If multiple threads are hang on a lock, are they maintained in a queue? When another thread signals the lock, will the first thread in the queue be released, or it randomly pick one thread to release?
Is this homework? Usually if it isn't homework, you would not have heard of those terms. :)
If you want actual code, you could try Beej's tutorial (assuming you're using POSIX pthreads). Just type "beej" into google.
If you want theory, you could try Wikipedia.
http://en.wikipedia.org/wiki/Multithreading
http://en.wikipedia.org/wiki/Mutex
http://en.wikipedia.org/wiki/Semaphore_(programming)