There are certain situations where processes can be competing for a shared resource in a system, where it is important for only one process to be allowed to access the resource. This is also called the critical section problem, and it is important in the context of operating systems and distributed computing. One easy example of the need for mutual exclusion is in an office or school environment with multiple computers hooked up to a shared printer. Print jobs must be scheduled so that when a certain print job is under execution, all others have to wait. It would be grossly unacceptable for pages from different jobs to be mixed up in printing, or for lines from different jobs to be mixed up on the same page. Multiprocessor cache-coherence protocols are another good example where mutual exclusion is needed--a cache cannot be read at the same...