UNIX Filesystems: Evolution, Design, and Implementation

How Many Versions of UNIX Are There?

Most versions of UNIX have stemmed from System V or BSD, with many taking enhancements from both. The 1980s saw a proliferation of versions of UNIX. Although it is difficult to give an exact figure on how many versions of UNIX have actually been produced, by the late 1980s it is safe to say that there were close to 100 different UNIX variants employed throughout the world. It is no wonder why UNIX has had its critics and not surprising that attempts at standardization have proceeded for much of UNIX's history.

Developing operating systems is a costly business, however, which has resulted in consolidation throughout the mid to late 1990s. On the low end, Linux and SCO variants tend to dominate while in the mid to high-end, Sun's Solaris, Hewlett Packard's HP-UX, and IBM's AIX account for most of the market share.

As time goes by there is likely to be further consolidation at the low to mid-range of PCs, workstations, and servers with Linux clearly leading the way. UNIX is still a clear leader at the high end of the market with Sun, HP, and IBM all having enterprise level capabilities in their UNIX offerings. While it is difficult to see further consolidation at this end of the market, only time will tell.