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What Is Unix? > What Is Unix? - Pg. 128

128 Chapter 6 systems that derive from or are similar to the operating system designed and implemented about 40 years ago at AT&T Bell Laboratories. Throughout this chapter, we'll use the term Unix to include official Unix-branded operating systems as well as Unix-like operating systems such as BSD, Linux, and even Macintosh OS X. History Years after AT&T's original implementation, there followed decades of aggressive market wars among many operating system vendors, each claiming that its operating system was Unix. The ever-increasing incompatibilities between these different versions of Unix were seen as a major deterrent to the marketing and sales of Unix. As personal computers grew more powerful and flexible, running inexpensive operating systems like Microsoft Windows and IBM OS/2, they threatened Unix as the server platform of choice. In response to these and other marketplace pressures, most major Unix vendors eventually backed efforts to standardize the Unix operating system. Unix is a Brand Since the early 1990s, the Unix brand has been owned by The Open Group. This organization manages a set of specifications with which vendors must comply to use the Unix brand in referring to their operating system products. In this way, The Open Group provides a guarantee to the marketplace that any system labeled as Unix conforms to a strict set of standards. Unix is a Specification The Open Group's standard is called the Single Unix Specification. It is created in collaboration with the Institute of Electrical and Electronics Engineers (IEEE), the International Standards Organization (ISO), and others. The specification is developed, refined, and updated in an open, transparent process. The Single Unix Specification comprises several components, covering core system interfaces such as system calls as well as commands, utilities, and a development environment based on the C programming language. Together, these describe a "functional superset of consensus-based specifications and historical practice." [2] Lineage The phrase historical practice in the description of the Single Unix Specification refers to the many operating systems historically referring to themselves as Unix. These include everything from AT&T's original releases to the versions released by the University of California at Berkeley and major commercial offerings by the likes of IBM, Sun, Digital Equipment Corporation (DEC), Hewlett-Packard (HP), the Santa Cruz Operation (SCO),