Domain/OS

Domain/OS was the operating system used by the Apollo/Domain line of workstations manufactured by Apollo Computers, Inc. during the late 1980s, as the successor to the one previously used, AEGIS. It was one of the early distributed operating systems. The operating system was supported for a short time by Hewlett-Packard, after they purchased Apollo, but they later ended the product line in favor of their HP-UX Unix variant.

AEGIS was distinctive mainly for being designed for the networked computer, as distinct from its competitors, which were essentially standalone systems with added network features. The prime examples of this were the filing system, which was fully integrated across machines, as opposed to Unix which even now draws a distinction between filing systems on the host system and on others, and the user administration system, which was fundamentally network-based. So basic was this orientation that even a standalone Apollo machine could not be configured without a network card.

Otherwise, AEGIS was similar to other workstations of the time, in that it used a high-resolution graphics screen and mouse to provide a type of Graphical user interface which, however, lacked almost all the tools (such as a directory browser) taken for granted today - the single exception being a Notepad-like text editor. Instead, the user was given a command-line window similar (although superior) to the DOS command line. This was not a problem since, usually, the machine would have been bought for a specific purpose, and the user would simply invoke the one or two packages he or she was interested in, typically a Computer-aided design or Desktop publishing system. Administrators were expected to work solely from the command line. The AEGIS command interface was similar to Unix, in that it had a shell which understood pipes, redirection, scripting, etc, and invoked other commands as separate programmes, but the actual commands themselves were designed to be easier to remember and use than their sometimes cryptic Unix equivalents, and wildcards were expected to be expanded by individual commands rather than by the shell itself. One noticeable and very useful feature was the ability to embed environment variables in symbolic links, which, for example, allowed the user to switch between different versions of Unix simply by setting the SYSTYPE environment variable accordingly; symbolic links then pointed to the correct versions of the files.

Domain/OS implemented functionality derived from both AT&T System V Unix and early BSD Unix systems. It improved on AEGIS by providing a core OS upon which the user could install any or all of three environments; AEGIS, System V Unix, and BSD Unix. This was done in order to provide greater compatibility with Unix; AEGIS version SR9, which immediately preceded Domain/OS (itself numbered SR10) had had an optional product called Domain/IX available, which provided a similar capability, but with some drawbacks, principally the fact that core administrative tasks still required AEGIS commands. Also, the SR9 permissions system was not fully compatible with Unix behaviour. Domain/OS provided new administrative commands and a more complex permissions system which could be configured to behave properly under any of the three environments. Domain/OS also provided an improved version of X-Windows, complete with VUE (HP s predecessor to CDE), but performance tended to be poor.

User upgrading from AEGIS SR9 to Domain/OS SR10 was slowed by the fact that many users saw no requirement; by increased disk space requirements; by new and more complex administration tools; by SR10 s poorer performance; and by the buggy nature of SR10.0, although later versions were much more reliable. However, later HP/Apollo machines (the DN10000, DN2500 and 4xx series workstations) could only run SR10.

Unlike many operating systems of the day, which were written in C programming language or assembly language, many Domain/OS components were written in Pascal programming language, although compilers available did include C programming language , C plus plus, Pascal programming language, and FORTRAN. All of the distributed administration features of Domain/OS were built around a remote procedure call system called NCS RPC. Though RPC was later end-of-lifed with the operating system, HP contributed RPC to the Open Software Foundation, which incorporated its Interface description language into their Distributed Computing Environment product, from which the same technology was later used for CORBA.