As you probably have noticed, there are some terms used in this documentation that are not exactly intuitive or immediately understood by today's programmers. In fact, you may have been wondering why such unusual terminology is used for functions or concepts that exist everywhere in the computer world. What, for example, are PPNs? Or random access files? Or ersatz devices? Or VUE? Or LIT files?
All of these things and more are explained by the story of A-Shell beginnings.
Back in the mid-to-late 1970s, a company called Alpha Microsystems (hereafter "AM") was created to bring to market the first multi-user micro computer—"micro" in this context meaning "computer on a (single integrated circuit) chip." You can read about AM and its computers on Wikipedia and on the S-100 website if you would like more information.
In addition to AMOS (Alpha Micro Operating System), the engineers at AM created an enhanced version of the BASIC language. Over the next ten or fifteen years, AM prospered and grew as small companies around the world realized they could obtain and manage an affordable business computer. With some few exceptions, all of the programs that made the computer popular and successful were written in AlphaBASIC. There were programs, and computer dealers, to perform every imaginable kind of computer task and business function. At the peak of its lifecycle, AM had some 300 computer dealers worldwide.
Unfortunately for AM and many firms in the computer business, including some big players such as HP, IBM and Digital Equipment Corporation, the personal computer revolution made small and mid-sized business computers largely obsolete. It didn't happen overnight, but the writing was on the wall: the future of computing was the PC.
But what about all those programs written in AlphaBASIC? How are they going to work, when the hardware they were built for is no longer available? Computer dealers and end-users had invested thousands of hours and tens or hundreds of thousands of dollars in their programs and their businesses, and now those investments were at serious risk.
What was needed was an AMOS work-alike—i.e., a compiler and operating environment that would allow those AlphaBASIC programs to run on non-AM hardware. Several firms created such systems, and A-Shell arguably was—or became—the best of them. The target audience for A-Shell was, of course, people and firms that were used to working with AlphaBASIC and AM computers. So of course A-Shell used the terms, language, concepts, file types, access methods, etc., that were in use in the AM world.
Following are descriptions and histories of some of those terms and concepts.
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