Speaking of Algol: RSRE Flex (info+connections sought) - cctalk

23 Jun 2026

Greetings,
Over the past several months I've been privileged to experience RSRE Flex,
an operating environment for PERQ workstations (and a few other bespoke
machines before that). Flex is interesting for being a networked
capability-based system with a hypertext-ish user interface, and everything
is implemented in Algol 68. Closures (in the programming language sense;
called "procedures" in Flex) are a fundamental abstraction similar in
importance to how files are fundamental to Unix*.*
Flex was developed in the late '70s and the '80s by the Royal Signals and
Radar Establishment, a research lab of the UK Ministry of Defence. Its
influence on computing has been limited as far as I can tell: the same
researchers went on to develop the Ten15 abstract machine which begat the
TenDRA compiler, and that might be most of the story. Nevertheless, the
system remains fascinating (I think) if you get the chance to learn about
it. I've collected some Flex materials here: https://mg-1.uk/flex/flex.html
In a few weeks I'll be giving a talk and demonstration of Flex to a
technically well-informed but otherwise unfamiliar audience. I can
certainly fill the time with rich technical details and descriptions of
things like Algol 68 and the PERQ, but I'd like also to have more to say
about the circumstances that brought Flex about and the ways people
encountered it at the time. I'm also hoping to gather information that
might lead to a public release of Flex someday (another thing I've been
working on behind the scenes).
So this message is a general request for information and connections:
- Did you or did someone you know work in computing at RSRE in the '70s and
'80s?
- Flex was shared with people outside of RSRE in the '80s, mainly
universities and colleges from what I can tell. Did you encounter Flex
running on a PERQ in one of these settings?
- Did you ever use Flex under any circumstances? What for?
Also:
- Flex contains numerical routines in both Algol 68 and PERQ microcode that
bear copyright assertions by Numerical Algorithms Group Ltd (now nAG,
nag.com). Does anyone know someone at nAG who would be a sympathetic person
to approach about the disposition of this very old IP?
Many thanks, --T