The TOPS-20 operating system by DEC —
the second proprietary OS for the PDP-10 — preferred by most PDP-10
hackers over TOPS-10 (that is, by those who were not
ITS or WAITS partisans).
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. The first in-house code name
for the operating system was VIROS (VIRtual memory Operating System); when
customers started asking questions, the name was changed to SNARK so DEC
could truthfully deny that there was any project called VIROS. When the
name SNARK became known, the name was briefly reversed to become KRANS;
this was quickly abandoned when someone objected that krans meant ‘funeral wreath’ in
Swedish (though some Swedish speakers have since said it means simply
‘wreath’; this part of the story may be apocryphal).
Ultimately DEC picked TOPS-20 as the name of the operating system, and it
was as TOPS-20 that it was marketed. The hacker community, mindful of its
origins, quickly dubbed it TWENEX (a contraction of ‘twenty
TENEX’), even though by this point very little of the original TENEX
code remained (analogously to the differences between AT&T V6 Unix and
BSD). DEC people cringed when they heard TWENEX
, but the
term caught on nevertheless (the written abbreviation ‘20x’ was
also used). TWENEX was successful and very popular; in fact, there was a
period in the early 1980s when it commanded as fervent a culture of
partisans as Unix or ITS — but DEC's decision to scrap all the
internal rivals to the VAX architecture and its
relatively stodgy VMS OS killed the DEC-20 and put a sad end to TWENEX's
brief day in the sun. DEC attempted to convince TOPS-20 users to convert
to VMS, but instead, by the late 1980s, most of the
TOPS-20 hackers had migrated to Unix. There is a TOPS-20 home page.