Flavors of UNIX Definition

The widely used term flavors of UNIX refers to the many Unix-like operating systems that have been developed based on the original UNIX that was written in 1969 by Ken Thompson at Bell Labs.

Fragmentation of UNIX occurred almost from the beginning. It was the result of both commercial pressures and differences in opinion among developers as to the way in which operating systems should behave.

Among the ways in which the various flavors of UNIX differ are (1) fundamental design, (2) commands and features, (3) the hardware platform(s) (i.e., processors) for which they are intended and (4) whether they are proprietary software (i.e., commercial software) or free software (i.e., software that anyone can obtain at no cost and use for any desired purpose).

Many of the proprietary flavors have been designed to run only (or mainly) on proprietary hardware sold by the same company that has developed them. Examples include:

  • AIX - developed by IBM for use on its mainframe computers
  • BSD/OS - a commercial version of BSD developed by Wind River for Intel processors
  • HP-UX - developed by Hewlett-Packard for its HP 9000 series of business servers
  • IRIX - developed by SGI for applications that use 3-D visualization and virtual reality
  • QNX - a real time operating system developed by QNX Software Systems primarily for use in embedded systems
  • Solaris - developed by Sun Microsystems for the SPARC platform and the most widely used proprietary flavor for web servers
  • Tru64 - developed by Compaq for the Alpha processor

Others are developed by groups of volunteers who make them available for free. Among them are:

  • Linux - the most popular and fastest growing of all the Unix-like operating systems
  • FreeBSD - the most popular of the BSD systems (all of which are direct descendants of BSD UNIX, which was developed at the University of California at Berkeley)
  • NetBSD - features the ability to run on more than 50 platforms, ranging from acorn26 to x68k
  • OpenBSD - may have already attained its goal of becoming the most secure of all computer operating systems
  • Darwin - the new version of BSD that serves as the core for the Mac OS X

This diversity has had both positive and negative effects. Most importantly, it has resulted in a healthy competition amongst them, which has been a major factor in the rapid improvement of the Unix-like systems as a whole.

However, at least in the past, it, made it difficult for them to compete with the Microsoft Windows operating systems except for very heavy duty corporate applications for which high stability and power were primary considerations. Unix-like operating systems continued to lose market share to the Microsoft systems throughout much of the 1990s as a result of the much lower cost, sometimes greater ease of use and rapid improvements in the latter. In fact, it was widely predicted that the dominance of Microsoft Windows was inevitable for most enterprise applications and that the role of the Unix-like systems would continue to diminish until they became just niche products.

What saved the Unix-like operating systems as a whole (but not the proprietary UNIXs) was the rapid maturation during the latter half of the 1990s of a new flavor -- Linux. This clone (i.e., a similar and compatible system but with all-original source code) overcame the disadvantages of the proprietary flavors by offering (1) very low cost (i.e., free), (2) the ability to operate on a wide range of platforms (everything from a supercomputer to a wristwatch), (3) the availability of the source code so that it could be easily and freely modified and improved by its users and (4) greater ease of use. This was all accomplished without sacrificing any of the power or stability that characterizes Unix-like operating systems.

Linux has continued to advance rapidly in terms of ease of use and other performance characteristics as a result of its open source (i.e., freely available source code) development model, and it has now become the dominant flavor of Unix-like operating systems.

The growth of Linux so far has been mainly at the expense of the proprietary flavors. However, there is widespread expectation that Linux will increasingly cut into the territory of the Microsoft operating systems as (1) its usability steadily improves, (2) businesses and other organizations become more familiar with its advantages and (3) more systems administrators become available for it.

It should be emphasized that Microsoft Windows is likewise not a single operating system, but rather a family of very different, often mutually incompatible, operating systems despite the superficial similarities. So perhaps they should likewise be referred to as flavors of Windows.

Created March 2004. Updated August 2, 2005.
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