Asynchrony
Dictionaries define the word synchronous to mean “happening at the same time.” For software and hardware systems, asynchronous has a different (but related) meaning: “happening independently of one another.”
We frequently encounter instances of synchrony throughout computer science. For example, clocks are said to be synchronous if they keep the same time (more specifically, if neither moves ahead of the other). Communication is said to be synchronous if one process makes a request of another and waits for a reply. In this sense, the exchange is considered synchronous because events happen in a dependent manner—a reply always follows a request. Similarly, code execution is synchronous: The next instruction comes after the previous ...
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