Any operating system built to resemble or emulate Unix, a.k.a Unix-like

"..one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. "
—[https://en.wikipedia.org/wiki/Unix-like|wikipedia]

"'Unix-like' is not approved by the [Open Group], which owns the UNIX trademark and administers the [Single UNIX Specification], with the "UNIX" name being used as a certification mark. They do not approve of the construction "Unix-like", and consider it a misuse of their trademark. Their guidelines require "UNIX" to be presented in uppercase or otherwise distinguished from the surrounding text, strongly encourage using it as a branding adjective for a generic word such as "system", and discourage its use in hyphenated phrases. (Not unlike [LEGO™]!)

Unix (or rather, UNIX), has a storied legacy, being developed within [Bell Labs] by the likes of [Ken Thompson], [Dennis Ritchie], and [Brian Kernighan]. Since devbelopment began in 1969 it's been copied, emulated, licenced and fought over in court. [holy wars|Arguments between geeks srill run] about what "Unix-like actually means, but most would agree that UNIX changed the way businesses could store, retrieve and manipulate data, and that other operating systems could be developed to take advantage of the mechanisms of Unix.

Unix-like systems started appearing in the late 1970s and early 1980s, with proprietary versions like Idris, UNOS, Coherent, and UniFlex aiming to bring UNIX-style functionality to businesses. [AT&T] began allowing commercial sublicensing of UNIX in [1979], and major vendors developed their own versions, such as [AIX], [HP-UX], [IRIX], and [SunOS]. Differences between these systems soon led to the creation of interoperability standards like [POSIX]. By the 1980s and 1990s, free and low-cost UNIX alternatives like [4.4BSD], Minix and [Linux] emerged, some of which later formed the basis for commercial Unix-like systems like BSD/OS and [macOS]. While BSD variants originated from AT&T UNIX via Berkeley, they have since replaced all AT&T code and, lacking official UNIX certification, are classified as "UNIX-like" rather than UNIX.

Of these, Linux has become the poster child of *nix OSes, being commonly used to run many (most?) data and web-hosting server systems, as well as pretty much all [supercomputer|supercomputers], and BSD now underpins [MacOS]. That said, BSD and Linux are both (increasingly since the 1990s) used as desktop operating systems following the development of many graphical tools and environments.

Originally developed by programmers for programmers, Unix had, and has, many tools useful to developers, but both it and the Unix-likes have evolved to meet the needs of the masses to a greater extent, to the point where MacOS and GNU/Linux systems have for many people taken over from the likes of Windows and previous iterations of Apple's OSes, by offering better stability and tooling for the dedicated few. Linux (and for some, [BSD]) in particular is popular among those geeks who relish being able to exercise finer control over their systems. I certainly appreciate being able to decide when and what to update on my system rather than being dictated to by Microsoft.

millions of words have been written about the history of Unix and its successors (I can rcommendone video history, [https://www.youtube.com/watch?v=AEsdyAeumVQ&pp=ygUMdW5peCBoaXN0b3J5|The History of UNIX], as a starting point, in addition to any interviews with Brian Kernighan and Dennis Ritchie. When [Linus Torvalds] developed his "hobby" [Linux kernel] there was a massive and enthusiastic response to his call for development help; clearly Unix had set standards for operating systems and showed there was a vacuum that needed filling in the other Unix-likes.

I have no doubt that, just as I am an advocate for Linux and [FOSS] in general, that there are those in the [BSD] world who are equally ardent about their choice of OS. *nix is here to stay; I encourage you to [winows 10|investigate] this brave new world and join us.

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