An old millrat here. I also have every flavor of Qbus PDP-11 operational.
RT-11 is a real time SO and could support forgraound background and with
a little help mutlitasking/multiuser (TSX). Biggest issue is 32mb max drive size.
Compacting a file is a PIP command using CCL.
Versioning was VMS V4 and later. The user could set the depth of versioning or
leave unlimited. Nothing like being able to edit File.txt and realize you good around;
file.txt;15 and go back the next day to ;14 as a recover.
I think TOPS20 also had versioning. Early TOPS10 did not (least in the 1971/2 timeframe).
I run VMS 5.4 and later on a array of MicroVAX systems some Qbus some table top
(3100 series). Those also have DECwindows. One stray runs Ultrix.
I was a late adopter to PC and dos/winders, mid 90s for that. Before it was RT-11,
RSX-11, UniX V6, Unix V7 on pdp-11, VMS on VAX, and CP/M.
I've been hacking CP/M since summer of '75 (v1.3). I have more than a dozen systems
running some version on 8080 though Z280 including CP/M+ and ZS/ZRdos.
Oh, EEF-2000 or E-ELF2000 is Bob's embedded ELF-2000 only the embedded version
cpu board was only ram and rom no displays and switches. IT did however mount
all the peripheral boards. I've referred to it and likely many have forgotten it. See the
ELF-2000 (files section) manual for details.