title: What is the original meaning of P and V operations in a context of a semaphore?
body: <p>Does anybody know why semaphore operations are called P and V? Every time I read a chapter on semaphores it says something like the following:</p>
  
  <p>In order for the thread to obtain a resource it executes a P operation. And in order for the thread to release a resource it executes a V operation.</p>
  
  <p>What does P and V stand for? Why they are not called wait and signal?</p>