mutex

I got an email offer to attend a web seminar ("webinar" :-& ) by some company selling Real-Time Operating Systems. A RTOS is an operating system that, unlike usual PC operating systems, can guarantee that some task will be performed before some future moment, if properly used. The guys were charging $39 for the exquisite privilege of attending their online seminar about mutexes and semaphores. Not any seminar about mutexes and semaphores, but an introductory seminar on mutexes and semaphores. Mutexes and semaphores are used so that two programs don't work on the same data at the same time, in order to avoid corrupting said data. Here's an introduction to mutexes and semaphores. Enjoy.
P.S. Some time ago a colleague was asked by a professor what "methods" does a semaphore have ("P" and "V"). "And which one of them increments the semaphore?" Dude, how the fuck should I know, I don't speak Dutch and I don't care for Verhogen! Can't you just call them increment and decrement or up and down like normal people?