A Brief History of UNIX and Its Derivative Operating Systems

UNIX, originally developed in 1969 at AT&T's Bell Labs by Ken Thompson, Dennis Ritchie, and Douglas McIlroy, began as "UNICS" and later became known as UNIX; its trademark is now owned by The Open Group, allowing only systems meeting the Single UNIX Specification to use the name.

In the 1970s AT&T recognized UNIX's commercial potential and began licensing its source code, leading to two dominant branches in the 1980s: Berkeley's BSD UNIX and AT&T's System V, from which many UNIX‑like variants emerged.

Sun Microsystems built SunOS (later Solaris) on BSD, while AT&T's System V gave rise to IBM's AIX and HP's HP‑UX. The article then surveys several mainstream UNIX‑like systems.

Mac OS, based on the XNU kernel (derived from BSD and Mach), transitioned from OS X to macOS and powers iOS devices; its source was released under the Apple Public Source License 2.0 in 2017.

AIX, IBM's UNIX implementation, conforms to the UNIX 98 standard and runs on IBM Power and RS/6000 platforms, offering extensive scalability and logical volume management.

Solaris, originally SunOS, evolved from BSD to System V, with Solaris 11 as the latest release; its source code for Solaris 11 was later opened as OpenSolaris under the CDDL license.

HP‑UX, derived from System V, runs on PA‑RISC and Itanium processors, while IRIX (SGI) and Xenix (Microsoft/​SCO) represent other historical UNIX variants.

A/UX, Apple’s UNIX for Macintosh, combined System V, BSD, and POSIX features, requiring a processor with a PMMU.

Linux, although not a direct UNIX descendant, originated from Minix and now powers a vast ecosystem of distributions (e.g., Fedora, Ubuntu, Red Hat, Debian, SUSE) and devices such as routers, smartphones, and embedded systems.