The UNIX Perspective

Rumors of UNIX's impending death are greatly exaggerated. Although there are those who equate column inches to vitality, this one-dimensional measure ignores the reality that often "no news is good news." Just as crime and heroism (and even "hype") are the stuff of headlines, little space is given to the uneventful.

Although there are many "niche players," the computer industry has become stratified into three layers. The high end includes the traditional mainframe market, long dominated by IBM. The low end--such as it is--contains a myriad of PCs, most of which are successors to IBM's original PC.

In between is the realm of "enterprise" servers and workstations. These systems run on hardware ranging from large PCs to massively parallel multicomputers. There is no dominant vendor in this realm, but UNIX has become the operating system of choice for users with large numbers of networked systems. Windows NT and its siblings have become contenders in a subrealm that might be called "local area servers" or "departmental application servers."

The Desktop
Where standard equipment for a white-collar office worker was once a typewriter and a telephone, the former has been replaced by a PC. In most cases, that PC runs one version or another of Microsoft Windows, but there is a sizable segment of the user community that does not. Millions of older systems run MS-DOS or early Windows versions and cannot economically upgrade to meet the requirements of current versions. Millions of other users prefer OS/2 or have chosen Macintosh systems or "true" workstations, which usually run UNIX. These preferences are the last bastions of individuality left in some organizations, which explains why attempts to mandate standard PC configurations often meet with strong resistance, especially among technical professionals.

The long and the short of it is that the desktop will remain a mixed and sometimes contentious environment for years to come. There is no indication that Microsoft's dominance will weaken anytime soon, but it is also clear that a significant number of people have determined that for technical or personal reasons they will not "do Windows."

A rapidly growing segment of students and computer professionals is now using Linux, a free UNIX implementation that includes Windows application programming interface (API) emulation along with "unbranded" implementations of several open systems technologies. It would be unwise to ignore the Linux crowd: They will be the ones making the computer-buying decisions in another decade.

UNIX
AT&T's Bell Laboratories was already among the largest minicomputer users 30 years ago. Bell engineers Dennis Ritchie and Brian Kernighan envisioned an operating system that would provide large-system capabilities on minicomputers for individual researchers. They had been involved in the AT&T/GE/MIT development of Multiuser Interactive Computing System (Multics) and thus included Multics features in their "UNIX" system. Where Multics had been developed in PL/I, Kernighan and Ritchie designed the C language and used it to create more than 90% of UNIX code. UNIX spread rapidly within Bell Labs, and AT&T soon made it available with very attractive licensing terms to educational institutions. Over time, UNIX has become the de facto standard minicomputer operating system within academic and research communities everywhere.

Open Systems Technologies
The open systems movement arose in the interest of providing guaranteed portability of applications from one platform to another. Because conversions between mainframe platforms--and even between dissimilar PC platforms--are expensive propositions, large users in government, academia, and commercial sectors demanded an alternative. At the least, they require APIs that are open, interoperable, and portable.

Early on, the definition of open systems varied from vendor to vendor, sometimes to incredible extremes. Even now, there are those who tout the Windows APIs as open, ignoring the significant fact that they are dictated by a single company without any public consultation with users or system vendors.

With users demanding an end to all this foolishness, the definition of "open systems" has become much clearer, and the various participants in what had been called "The UNIX Wars" have come to terms. There might never be a single definition that satisfies both the purists and the pragmatists of the open systems community; however, several basic principles apply to any definition of "open:"

• The API definition must be in the public domain or available to anyone at a modest price.
• The API definition cannot be unilaterally changed or influenced by any one vendor.
• The vendor must not become a "single point of failure."
• Reference implementations must exist on distinctly different hardware platforms.
• Exhaustive tests must exist to prove conformance of any given implementation.

The Windows APIs violate the first three points. These APIs have undergone incompatible changes during each of their last three incarnations, and there is no indication that the future will be more disciplined.

Because of these incompatibilities, Windows upgrades have given the appearance of "churning" the user base to force application upgrades. That's merely a bad situation at the single-
system level, but forcing a group of networked systems to upgrade simultaneously is unacceptable.

The third point has to do with application survivability if there is the failure--or breakup--of the vendor on which the application depends. I don't expect anything drastic to happen to Microsoft anytime soon, but the basic point remains: You shouldn't put all your eggs in one basket.

Other measures of open systems have been suggested, but the five listed protect the basic interests of the user community. Those interests center around software portability and interoperability across a wide variety of hardware platforms.

The user community plays an important role in this process; it's not driven solely by the vendors. This user involvement reflects a fundamental difference between the open systems part of the marketplace and the mainframe and desktop arenas. Unlike the other two, where a single company has become dominant, there is actual competition among open software vendors.

The intent of open systems is to specify and make available a set of common APIs. These APIs should work exactly the same way on a wide variety of systems, some of which run operating systems other than UNIX. Applications that adhere to the standard APIs should compile and operate correctly on any conforming system.

This discussion of open systems is not specifically about UNIX. Other open technologies take precedence over the operating systems on which they are implemented. Two of these technologies are Motif extensions to the X11 Window System and the Distributed Computing Environment. DCE provides a uniform and securable client/server infrastructure to applications running on everything from IBM mainframes to dozens of UNIX and other enterprise server systems to Windows NT and Macintosh PCs. Both of these technologies were specified and implemented under the guidance of Open Software Foundation (OSF).

OSF was created to guide the development of open technologies that can be included in products from multiple vendors. With the agreement upon a common UNIX interface specification and conformance testing, OSF's sponsors and members in North America, Europe, and Asia are a remarkable cross-section of the computer industry and its major users.