Semaphore (programming) - Function Name Etymology

Function Name Etymology

The canonical names P and V come from the initials of Dutch words. V stands for verhogen ("increase"). Several explanations have been offered for P, including proberen for "to test," passeer for "pass," probeer for "try," and pakken for "grab." However, Dijkstra wrote that he intended P to stand for the portmanteau prolaag, short for probeer te verlagen, literally "try to reduce," or to parallel the terms used in the other case, "try to decrease." This confusion stems from the fact that the words for increase and decrease both begin with the letter V in Dutch, and the words spelled out in full would be impossibly confusing for those not familiar with the Dutch language.

In ALGOL 68, the Linux kernel, and in some English textbooks, the P and V operations are called, respectively, down and up. In software engineering practice, they are often called wait and signal, acquire and release (which the standard Java library uses), or pend and post. Some texts call them procure and vacate to match the original Dutch initials.