Twenex

Twenex was the TOPS-20 operating system by DEC - the second proprietary OS for the PDP-10. TOPS-20 began in 1969 as Bolt, Beranek & Newman's TENEX operating system using special paging hardware. By the early 1970s, almost all of the systems on the ARPANET ran TENEX. DEC purchased the rights to TENEX from BBN and began work to make it their own....
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