TOPS-20
More info
- Creator
- Digital Equipment Corporation
- Released
- Type
- Operating system
- Predecessor
- TENEX (BBN)
DEC's operating system for the DECSYSTEM-20 — home to much of ARPANET-era hacker culture, killed off with its own hardware.
It was not DEC's invention: the company bought TENEX from BBN, who had built it on the PDP-10 with paged virtual memory, and renamed it in 1976. Its command interpreter, EXEC, had a property that was sensational at the time — it completed command names and filenames when you pressed escape, and listed the options on a question mark. Tab completion, a decade before Unix shells got it.
Many of the machines on the ARPANET ran TOPS-20 or its relative TOPS-10, and a large share of the vocabulary in the Jargon File originates there. When DEC cancelled the PDP-10 line in 1983 in favour of the VAX, the system died with the hardware. Emulators such as SIMH still run it, for anyone curious how a friendly mainframe felt.