Learn in the textbookRepresentative Types of Operating Systems
DefinitionUNIX is an OS born at AT&T Bell Labs in the late 1960s that can serve many users and run many processes at the same time.
ExplanationIt offered multi-user operation, where many people share one computer at once, and multitasking, where several programs run in parallel, from an early stage, so it has long been used on servers and workstations that need stability. Its design ideas were carried into many later operating systems, and both Linux and Mac OS belong to this line.
AnalogyIt is like the original shop of an old restaurant whose recipes were passed on to many branches, so you can taste its methods without visiting the first shop.
Memory hookAn earlier, larger OS project was called Multics, from "multi"; UNIX swapped that for "uni" as a pun, and the name stuck.