TOPS-20

TOPS-20 was a timesharing operating system for 36 -bit computer family from Digital Equipment Corporation, which could be used on the newer CPUs KL10 and KS10 the PDP-10. The combination PDP -10 and TOPS-20 was introduced as DECsystem20 from 1976, the marketing ended with the setting of the entire 36 -bit product line in 1983.

History

TOPS-20 was not a DEC - house development, but was based on a system that (BBN ) had developed for his own use on the older PDP-10 CPUs in the company Bolt Beranek and Newman. This system, known as the TENEX ( TEN Acronym EXtended ), supported from the beginning virtual memory management (some with a self-developed paging hardware ). In addition, the commands were very long ( almost sets), but they could - as long as clearly - be shortened, there were already the possibility to use AutoComplete of the commands Escape key ( as later with many Unix shells such as tcsh in which the initial letter t is an abbreviation for TENEX ). TENEX has long been used at many universities in the United States instead of TOPS -10 and was appreciated even within the DEC. BBN had many attempts to incorporate both TENEX and the self-developed hardware additions in the DEC product line, but without success. However, DEC acquired in 1973 the rights to TENEX, but had no immediate visible impact on the business policy. However, it was immediately started with the development of TENEX, which DEC internally used many different code names to confuse the competition.

The next generation of the PDP -10 CPUs, the 1974 market-ready KL10, the DEC developer had built a paging hardware that met all requirements, needed the TENEX for its virtual memory management. But even this new machine was initially only with TOPS -10 on the market. It was not until later in January 1976, a system was offered with an OS TOPS- 20 without was that officially announced that it was a development of TENEX. Both DEC - internally as well as with the users but sat down for the new operating system of unofficial name TWENEX by. As can be seen from the development, it was at TOPS- 20 does not, as suggested earlier, a further development of TOPS- 10th Both operating systems were developed parallel to the 1980s.

Properties

TOPS-20 was at the time his show properties that have been implemented in other operating systems partially until years later:

• Virtual memory management with demand paging
• Directory / file names have up to 39 characters long ( see VMS)
• Version numbers for files (see VMS)
• Auto-completion of commands (see tcsh )
• Command interpreter running in an ordinary user process (see Unix)

Main markets

The 36 -bit family of DEC was initially used mainly at universities and non-university research institutions. While in the United States, operating systems TOPS -10 and TENEX were about equally represented here, dominated at that time in Europe TOPS- 10th With the advent of TOPS-20 TENEX many installations are quickly transferred to TOPS -20 in America, a similar effect could not occur in Europe because of the small TENEX distribution.

Parallel to this traditional market, the DECsystem20 with TOPS-20 has secured a niche in the commercial environment because of its good transaction services. The advantages of interactive working with inexpensive ASCII terminals connected in series were initially recognized and used only in an academic environment, however, innovative companies used this technique also. Customers included hospitals and freight forwarders. The success in the commercial market could be further increased, as came with TOPS- 20 with the DECsystem2020 based on the KS10 processor, a computer from the class of superminis on the market.