Interesting! All I know of RSRE is that they did a bunch of work on Algol 68
implementation, including a subset compiler called Algol68RS.
paul
> On Jun 23, 2026, at 5:33 PM, Tom Stepleton via cctalk <[email protected]>
> wrote:
>
> 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
