Ken and Dennis was first developed at Bell Labs Unix, and the subsequent 10, Unix in academic institutions and large enterprises has been widely used,

Ken and Dennis was first developed at Bell Labs Unix, and the subsequent 10, Unix in academic institutions and large enterprises has been widely used, then the UNIX owner of AT & T's cheap or even free to license Unix source code will be authorized To academic institutions doing research or teaching purposes, many organizations on the basis of this source to be expanded and improved, forming a so-called Unix "variant (Variations)", these variants in turn has promoted the development of Unix, of which the most famous One variant from the University of California at Berkeley BSD development of the product.

AT & T was aware of the commercial value of Unix, Unix source will no longer authorized to academic institutions, and before the Unix variant and its statement of the rights of copyright. BSD Unix variant of Unix in the historical development of considerable influence, many commercial manufacturers use as the basis for many commercial Unix. Increase the use of the main version of BSD version of the method of identification, such as the 4.2 BSD, 4.3BSD, in the original version is also available on the basis of derivative version, these versions usually have their own names, such as the 4.3 BSD-Net / 1,4.3 BSD-Net / 2, and so on. Its growing influence has finally aroused the concern of AT & T, began a protracted copyright lawsuit, this lawsuit has been hit AT & T will own laboratory sell Unix systems, the new Novell took over the company adopted a Comparing open-minded approach, allowing freedom of Berkeley released its BSD, but the premise must be from AT & T completely remove the code, so the birth of the 4.4 BSD Lite version, this version does not exist because of legal issues, 4.4 BSD Lite to become a modern BSD systems The base version. Although later, non-commercial version of the UNIX system and after a lot of evolution, but the end of the day, are built on the BSD version (Linux exception). So from this perspective, 4.4 BSD are all free version (Free Edition) Unix foundation, which Linux and Unix V and a common Unix operating system this bright night sky.

BSD in development have gradually led to the three main branches: FreeBSD, OpenBSD and NetBSD.

After decades, Unix is constantly changing, constantly changing its owners, authorized the number is increasing. Unix has the copyright to all AT & T, after Novell has a Unix, Novell will again after the sale of the copyright to the SCO (the fact that the two sides remain in dispute). There are many large companies have made in the mandate of Unix, developed its own Unix products, such as IBM's AIX, HP's HPUX, SUN's Solaris and SGI's IRIX.

Unix because of its secure, reliable, efficient powerful features in the server has been widely used. Until the GNU / Linux before the start of popular, Unix is scientific computing, the mainframe, super computers and other operating systems used by the mainstream.