What is UNIX ®?

In 1994 Novell (who had acquired the UNIX systems business of AT&T/USL) decided to get out of that business. Rather than sell the business as a single entity, Novell transferred the rights to the UNIX trademark and the specification (that subsequently became the Single UNIX Specification) to The Open Group (at the time X/Open Company). Subsequently, it sold the source code and the product implementation (UNIXWARE) to SCO. The Open Group also owns the trademark UNIXWARE, transferred to them from SCO more recently.
Today, the definition of UNIX ® takes the form of the worldwide Single UNIX Specification integrating X/Open Company's XPG4, IEEE's POSIX Standards and ISO C. Through continual evolution, the Single UNIX Specification is the defacto and dejure standard definition for the UNIX system application programming interfaces. As the owner of the UNIX trademark, The Open Group has separated the UNIX trademark from any actual code stream itself, thus allowing multiple implementations. Since the introduction of the Single UNIX Specification, there has been a single, open, consensus specification that defines the requirements for a conformant UNIX system.

Introduction

Many names have been applied to the work that has culminated in the Single UNIX Specification and its attendant X/Open UNIX brand. It began as the Common API Specification, became Spec 1170, and is now the Single UNIX Specification published in a number of X/Open Common Applications Environment (CAE) volumes. This paper briefly describes the history of Spec 1170, and its journey to becoming the Single UNIX Specification, along with the organization of that specification.

HistoryPreviously the UNIX operating system has been a product with four elements (Figure 1); the specification (e.g. SVID) , the technology (e.g. SVR4), the registered trade mark (UNIX), and the product (e.g. UNIXWare)

With the Single UNIX Specification, there is now a single, open, consensus specification that defines a product. There is also a mark, or brand, that is used to identify those products that conform to the Single UNIX specification. Both the specification and the trade mark are now managed and held in trust for the industry by X/Open Company. There will be many competing products, all implemented against the Single UNIX Specification, ensuring competition and vendor choice. There will be a limited number of technology suppliers, which vendors can license and build there own product, all of them implementing the Single UNIX Specification. . Buyers can expect each of these products to carry the X/open UNIX brand as an guarantee of conformance to the specification and that the vendor stands behind a quality product.

UNIX 93 applies to UNIX system products which pre-date the Single UNIX Specification.
UNIX 95 applies to UNIX system products which conform to the Single UNIX Specification.
UNIX 98 applies to UNIX system products which conform to the Single UNIX Specification , Version 2.
UNIX 03 applies to UNIX system products which conform to the Single UNIX Specification , Version 3.