Answer 5—The one key concept required to successfully share data among asynchronous processes is the ability to do atomic updates. An atomic update means that one process can update a memory object (variable or structure) in such a way that no other process can read it in a partially updated state.

Sometimes, the only type of object that can be updated atomically is a single machine word, which might be anywhere from 8 to 32 bits. Mutual-exclusion (a.k.a. “mutex”) protocols have been developed that allow such a variable to protect a larger shared structure such as a FIFO that can’t otherwise be updated atomically.

Contributor: David Tweed