Unix, is a family of multi-tasking, multi-user computer operating systems, that originally derived from the AT&T UNIX, the development started in the 1970s by Ken Thompson, Dennis Ritchie, and others at the Bell Labs research center. Initially, Unix intendedly designed for use inside the Bell System.
The AT&T licensed Unix to outside parties from the late 1970s, leading to a variety of both academic, and commercial variants of Unix from vendors such as the Berkeley (BSD), University of California, IBM (AIX), Microsoft (Xenix), and Sun Microsystems (Solaris).
In the early 1990s, AT&T finally sold its rights in Unix to Novell, which then sold its Unix business to the Santa Cruz Operation (SCO) in 1995, but the Unix passed to the industry standards consortium “The Open Group”, which allows the use of the mark for certified OS compliant with the Single Unix Specification (SUS).
Among these is Apple’s macOS, which is also one of the popular Unix version with the largest installed base as of 2014. It was originally meant to be a convenient platform for programmers developing programs to be run on it and on other systems, rather than for non-programmer users.
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Top Most Popular Free Unix-Like Operating Systems!
A Unix-like operating system, that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-like software is one that behaves like the corresponding Unix command line or shell.
There is no standard for defining the term, and some difference of opinion is possible as to the degree to which a given OS or application is “Unix-like”. The “Unix-like” systems started to appear in the late 1970s and early 1980s.
Different proprietary versions of Unix, such as Idris (1978), UNOS (1982), Coherent (1983), and UniFlex (1985), all aimed to provide businesses with the functionality available to academic users of Unix OS.
Many Unix-like operating systems have arisen over the years, in which Linux is one of the most popular, having displaced Unix SUS-certified on many server platforms since its inception in the early 1990s.
Various free, low-cost, and unrestricted substitutes for Unix emerged between 1980s to 1990s, including BSD, Linux, and Minix. Other most active Unix-like operating systems are:
MenuetOS is a real-time, pre-emptive, and multi-processor Operating System in development for the PC written entirely in 32/ 64 bit assembling languages.
Menuet64 is released under License and Menuet32 under the GPL License. It supports 32/ 64 bit x86 assembly programming for smaller, faster and less resource hungry applications.
MenuetOS isn’t based on other OS nor has it roots within UNIX or the POSIX standards.
NetBSD is also an open source, secure, and highly portable, Unix-like free operating system. Available for a wide range of platforms, from large-scale servers and powerful desktops to hand-held and embedded devices.
NetBSD’s clean design and advanced features makes it excellent for use in both production and research environments, and the source code is freely available under a business-friendly license.
The OpenBSD project produces a free, multi-platform, UNIX-like operating system. Their efforts emphasize portability, standardization, correctness, proactive security and integrated cryptography.
As an example of the effect it has, the popular OpenSSH software comes from it. OpenBSD is freely available from our download sites. OpenBSD is developed entirely by volunteers.
Some of these have in turn been the basis for commercial “Unix-like” systems, such as BSD/ OS and macOS.
Dennis Ritchie, one of the original creators of the Unix OS, expressed his opinion that Unix-like systems, such as Linux are de facto Unix systems.
Eric S. Raymond and Rob Landley have also suggested that there are three kinds of Unix-like systems:
Genetic UNIX: Those systems with a historical connection to the AT&T code-base.
Trademark or branded UNIX: These systems, largely commercial in nature; have been determined by the Open Group to meet the Single Specification of UNIX, and are allowed to carry the UNIX name.
Functional UNIX: Broadly, any Unix-like operating system that behaves in a manner roughly consistent with the specification of the UNIX system, including having a program which manages your login and command line sessions.
More specifically, this can refer to operating systems such as Linux or Minix, that behave similarly to a Unix system but have no genetic or trademark connection to the AT&T code-base.