back to article Think that spreadsheet in your company's accounts dept is old? 70 years ago, LEO ran the first business app

Seventy years ago this week, LEO, the world's first computer for business, ran one of the first enterprise applications after several experimental test runs. Built for British catering and tea shop giant J Lyons, the Lyons Electronic Office, dubbed LEO, took inspiration from the Cambridge EDSAC, which ran its first programs in …

  1. Wally Dug
    Pint

    Trailblazers

    With absolutely no offence meant to Lisa McGerty, LEO project manager at the Centre for Computing History, but the slightly untrustworthy AI computer in Duncan Jones's movie Moon (and voiced by Kevin spacey - 'nuff said) is called GERTY.

    I am fascinated, however, at the foresight of the people at Lyons for taking that leap in seeing how one of these electronic "brains" could possibly help them with their business.

    1. DJV Silver badge

      Re: Trailblazers

      I recommend the book "A Computer Called LEO" by Georgina Ferry for a fascinating insight into the history of LEO.

      1. anothercynic Silver badge

        Re: Trailblazers

        Indeed! A great book it is too!

      2. Tom 7 Silver badge

        Re: Trailblazers

        I read that book not long after it came out. At the time I was helping to manage the IT for several hundred Windows machines and a few bits of big iron. It didnt amaze me that a few thousand valves and some competent programmers pissed all over a few billion transistors and some MS shit.

        1. Steve Davies 3 Silver badge
          Thumb Up

          Re: Have an upvote for

          the words

          "Some MS shit"

          Perfect.

    2. This post has been deleted by its author

    3. Anonymous Coward
      Anonymous Coward

      Re: Trailblazers

      While my mother worked as a Nippy, my father implemented LEO (for Payroll processing) at Fords.

  2. Neil Barnes Silver badge

    very little hardware remains

    My late father worked for Lyons - as a transporter of cake over the Pennines, in no way connected with the IT or office side. One day when I was ten or eleven - early seventies - he brought home what he told me was a damaged and discarded part of the LEO system. I have no idea how he came by it, but I played with it for a while.

    It consisted of a single circuit board with edge connectors at one end, thyratrons on the PCB, and a Nixie tube on one side. I discovered in (much) later research it was actually a display/adder board for an Anita MK8 calculator... but for a while, for a while...

    1. Spoobistle

      Re: very little hardware remains

      I don't know about LEO 1, but I recall having some LEO 3 circuit boards as part of a surplus "bargain parcel" bought from one of the advertisers in the back of Practical Electronics (possibly Greenweld) in the 1970s. Lots of GET102 transistors, germanium diodes etc for the industrious schoolboy to ruin with a hot soldering iron!

      1. Neil Barnes Silver badge
        Happy

        Re: very little hardware remains

        Ah the days of my youth. Greenweld...

        1. Anonymous Coward
          Anonymous Coward

          Re: very little hardware remains

          Ah, the days of my youth. Practical Electronics... and the 1970s.

        2. Anonymous Coward
          Anonymous Coward

          Re: very little hardware remains

          "Greenweld"

          An uptick for you.

          My 90 year old mum was reminding me of my trips there just the other day - as we drove past where the shop once was.

          1. Tom 7 Silver badge

            Re: very little hardware remains

            Greenunweld shirley - just remembered removing components from boards I got from them.

    2. Solviva

      Re: very little hardware remains

      Ahh cake - just say no kids!

  3. Howard Sway Silver badge
    Mushroom

    "LEO was also kept busy ... calculating missile trajectories for the Ministry of Defence"

    According to the excellent linked history article.

    Hopefully we don't get a "Who Me?" article by someone who mixed up the punch cards for this with the stock ordering system, explaining the complete disappearance of the Lyon's corner houses from our streets.

    1. Wally Dug
      Coat

      Re: "LEO was also kept busy ... calculating missile trajectories for the Ministry of Defence"

      But the flip-side is that, due to the punch card mix-up, the MoD invented Eton Mess...

      (Old Glasgow joke: Am I right, or am a wrang?)

      1. Screwed

        Re: "LEO was also kept busy ... calculating missile trajectories for the Ministry of Defence"

        I heard it as a Morningside joke. The accent seems to work better...

  4. Moldskred

    Seventy years ago this week...

    And about sixty-nine years and eleven months ago this week, a computer programmer made the first complaint about dealing with legacy code.

    1. Stuart Castle Silver badge

      Re: Seventy years ago this week...

      And about sixty-nine years, 11 months and 3 weeks ago this week, a user was advised to turn it off and on again to solve a problem.

  5. Anonymous Coward
    Anonymous Coward

    Not forgetting Turing

    And the current Wikipedia 'On This Day' includes...

    "1936 – English mathematician Alan Turing published details of the Turing machine (model pictured), a basic abstract symbol-manipulating hypothetical device that can simulate the logic of any computer algorithm."

    1. bombastic bob Silver badge
      Devil

      Re: Not forgetting Turing

      it must be a good eay for computing.

      If you follow the link to the B&W original pic of the LEO and zoom it in to 300% or so you can see the vacuum tubes in the right-most uncovered panel. The ones on top look like octal types (maybe rectifiers) and most of them look like 7 or 9 pin miniature types.

      Tubes/valves eventually got smaller (micro-miniatures) until transistors were reliable and fast enough to replace them.

      The only real limiter on speed would have been wire length and the mercury delay line RAM. Tubes could operate at hundreds of megahertz and gigahertz long before transistors. But the size and wire length would limit them. 1 meter of wire and you can no longer exceed 150Mhz, for example (assuming half a wavelength to be your limiter, round-trip logic pulse time basically)

      1. Tom 7 Silver badge

        Re: Not forgetting Turing

        I did see a design for silicon 'tubes' - the cathode was replaced with a sharp point to induce a very strong electric field to induce electron discharge and then just miniature other valve stuff. Not sure how long the cathodes lasted but it did look promising for vacuum ICs.

      2. herman Silver badge

        Re: Not forgetting Turing

        Nuvistor miniature tubes were used in TV sets and looked much the same as transistors. They could work up to 3 GHz: https://www.aeronetworks.ca/2020/08/rtl-sdr-weather-satellite-preamplifier.html?m=1

  6. Missing Semicolon Silver badge

    Shame

    How can you fail at tea-shops in the UK?

    1. DJV Silver badge

      Re: Shame

      It takes skill and a lump or two of sugar.

    2. 2+2=5 Silver badge

      Re: Shame

      > How can you fail at tea-shops in the UK?

      Probably something to do with paying all their taxes and not buying tea from a parent company based in Switzerland.

    3. anothercynic Silver badge

      Re: Shame

      It's called "changing fashions"... All revealed in the book about LEO.

      1. Anonymous Coward
        Anonymous Coward

        Re: All revealed in the book about LEO.

        But is there not a book mainly about Tea Shops, albeit also containing a tangential summary of some early computing machines? :-)

  7. Contrex

    The first working computer I ever saw was the LEO 3 at John Humphries House, Greenwich, which was shared by the London Boroughs of Bexley, Greenwich and Southwark. Its services were also used by the Forest and Bexley Hospitals and the Bloodstock Agency. I was aged 13 and was part of a group of third-formers at Alleyn's School who went there on an educational visit in 1965. The school also funded the Electronics Society to build a 'computer' based on relays like those of Konrad Zuse.

  8. A Non e-mouse Silver badge

    There's an excellent book on the history of Leo: A Computer Called LEO.

    It describes how, for once, the board of Lyons understood IT. They could see that LEO could drastically improve currently manual computations: But they could also see that if LEO broke the business would be stuffed. So they insisted that a second LEO was built, just in case.

    1. Antony Shepherd

      Good to see someone else mentioning that book, it's a good read and I'd recommend it to anyone. There's a great bit about how at one time they bought a load of cheap American calculating machines, so they'd convert all their figures to decimal, run the figures through the calculating machines, and convert the results back to the original non-decimal units, and that was still quicker and more accurate than doing all the calculations by hand.

      From there LEO was just the next step.

      1. DRue2514

        Also recommend that book. I seem to remember that there was a lot about the individuals that drove the project forward and there are many lessons in there that are very relevant still today.

      2. Kubla Cant Silver badge

        convert all their figures to decimal, run the figures through the calculating machines, and convert the results back to the original non-decimal units

        In about 1965 I worked in a City Treasurer's office where we did exactly that in order to perform calculations on an electronic calculator. IIRC we had lookup tables for conversion between shillings & pence and decimal pounds written out on sheets of card.

  9. Franco Silver badge

    There's probably still legacy code to support LEO somewhere in Windows 11......

    1. Arthur the cat Silver badge

      I wonder if there's a Raspberry Pi based LEO emulator?

      1. bombastic bob Silver badge
        Linux

        interesting - SImH might be capable. anyone have the manuals and wanna write it?

        There's a github repo HERE if anyone wants to contribute...

      2. LateAgain

        Beat me to it ;-)

        P1 emulated on a PI

    2. LDS Silver badge
      Joke

      It's far easier that some *nix specs are based on some LEO requirements and carried over in Linux....

    3. Tom 7 Silver badge

      There's probably still legacy code to disable LEO somewhere in Windows 11.

    4. gerryg

      Surely Leonix is out there somewhere.

  10. Doctor Syntax Silver badge
    Pint

    Oh.

    Shit.

    It must have been about 50 years ago, maybe a year or so more, that I got sent on a FORTRAN course. That means that I've been dealing with this stuff on and off for most of the time since Lyons started commercial computing. It's a sobering thought. So sobering I need...

    1. Arthur the cat Silver badge

      <yorkshireman>A course? Luxury!</yorkshireman>

      50 years ago I got given an existing program to calculate semiconductor electron band structure plus a yellow Algol-68R manual and was told to add spin-orbit coupling to the calculations.

      1. Doctor Syntax Silver badge

        Five days. As it was compulsory I wasn't keen* and I was accompanying SWMBO on a field trip to Scotland. Not being in a hurry to get back I missed the first day. I'm not sure what they did on the first day but it couldn't have been much. The remaining four days were enough to show it was all straightforward. Maybe things went downhill a little after that.

        * Compulsory was always bad news, right from gym at school.

    2. HildyJ Silver badge
      Windows

      1968 - IBM 1401 Autocoder and BASIC. Ah, the smell of punch cards in the morning.

      But I wouldn't compare myself to LEO programmers. I'm not sure what they wrote in since the Autocode language (not to be confused with IBM Autocoder) was not ported to EDSAC until much later.

      https://en.wikipedia.org/wiki/Autocode

  11. Lars Silver badge
    Happy

    The first is such a nice word.

    Konrad Zuse (German: 22 June 1910 – 18 December 1995) was a German civil engineer, pioneering computer scientist, inventor and businessman. His greatest achievement was the world's first programmable computer; the functional program-controlled Turing-complete Z3 became operational in May 1941. Thanks to this machine and its predecessors, Zuse has often been regarded as the inventor of the modern computer.

    In 1941, he founded one of the earliest computer businesses, producing the Z4, which became the world's first commercial computer. From 1943 to 1945 he designed Plankalkül, the first high-level programming language.

    Due to World War II, Zuse's work went largely unnoticed in the United Kingdom and the United States. Possibly his first documented influence on a US company was IBM's option on his patents in 1946.

    https://en.wikipedia.org/wiki/Konrad_Zuse

    1. Yes Me Silver badge
      Headmaster

      Re: The first is such a nice word.

      "Zuse has often been regarded as the inventor of the modern computer."

      And often not. The Z3 did not store its program internally in its working memory (the "tape" in a Turing machine). Zuse did not know about Turing machines until after WW II, in fact. Anyway, Z3 was not Turing-equivalent in that sense (program and data stored in the same memory). Eckert and Mauchly invented that idea, von Neumann wrote it down (and knew of Turing's work) but Williams & Kilburn at Manchester actually built the first computer with an internally stored program (running in June 1948). Wilkes at Cambridge built the second one, EDSAC.

      Zuse was an inventor, as was Atanasoff. But it took all of those named above to actually build the first two.

      1. fg_swe

        Zuse, Binary Numbers

        As with the bike and the telephone, many countries claim to be first.

        Zuse's great idea was to use binary numbers instead of decimals.

        According to

        https://de.wikipedia.org/wiki/Zuse_Z4

        it already had a conditional jump instruction.

        Zuse also had floating point numbers, which is impressive.

        As the article is about "commercial computers", it could be argued that Zuse's work was initially military and then scientific. Not "commercial".

        1. Lars Silver badge
          Happy

          Re: Zuse, Binary Numbers

          @fg_swe

          This story is about the LEO and the year 1951 and I have no doubt computers were in commercial use then not only in Germany too.

      2. anonymous boring coward Silver badge

        Re: The first is such a nice word.

        It's still a programmable computer. There's no requirement to modify the code dynamically to be a computer. The program was stored on a tape, just like with later machines.

        https://en.wikipedia.org/wiki/Z3_(computer)

        Interestingly:

        "In 1937, Claude Shannon introduced the idea of mapping Boolean algebra onto electronic relays in a seminal work on digital circuit design. Zuse, however, did not know of Shannon's work and developed the groundwork independently[10]: 149 for his first computer Z1, which he designed and built from 1935 to 1938."

      3. Lars Silver badge
        WTF?

        Re: The first is such a nice word.

        @Yes Me

        "Zuse did not know about Turing machines until after WW II".

        What the hell has that to do with anything.

        Do you think we would have no computers today had Turing never been born or that Zuse needed to know about Turing to design his computers.

  12. msobkow Silver badge

    It is hard to believe computing is only 13 years older than me, at least in terms of the first "real" vaccuum-tube computers. No wonder I feel like I've spent my whole life growing up with the technology... :)

  13. DS999 Silver badge

    Can someone explain

    Just what the heck a "bakery valuation job" is, and why it was so demanding it could have possibly made sense to replace the person (people?) doing it with a machine back when they cost millions to own and operate and were dumber than my mid 90s era microwave oven?

    1. Neil Barnes Silver badge

      Re: Can someone explain

      Well I can't explain the term directly but I know that my late father's job (above) was to deliver pallets of cakes from the bakery in Wakefield to a number of delivery hubs on the other side of the Pennines. At the depot he got busy with a fork lift truck transferring pallets from his twenty-five ton truck to smaller trucks that delivered to individual outlets; each pallet was different and each held cakes for often multiple retailers.

      The swearing was loud and colourful if the wrong pallet ended up in wrong place on the feeder truck, or (oh no!) on the wrong feeder entirely. It didn't help that there were dozens of products and they were rarely the same on successive days...

      I can only assume that, probably on a couple of day's notice, hordes of one-man shops as well as the supermarkets placed their order for cakes and that a bevy of office staff went through the orders adding things up so they could tell the bakery, right Joe, we need fourteen thousand swiss rolls, six thousand Kunzle cakes, and so on, and someone else generated pick and place lists to load the pallets and label them by delivery and feeder truck.

      At the time, the cake baking was industrialised but I don't recall any great shelf life, so stuff was pretty much baked to demand.

      Not a simple thing to do, unless you're a computer...

      (Yes, I did occasionally go along with my father for the hell of it, on a Friday night when I didn't have school the next day.)

      (Also, the happiest I ever saw my father was when he came home and announced that the Kipling's factory had just burned down... overtime for months!)

      1. Pascal Monett Silver badge

        Indeed. An explanation like that puts in sharp relief why such a technology would be welcomed with open arms by a company. The improvement in delivery efficiency alone probably reimbursed the cost of the whole thing.

        1. herman Silver badge

          The first business programs were basically electronic Cardex systems.

      2. Doctor Syntax Silver badge

        Re: Can someone explain

        On top of that ingredient orders would also have to be managed. Then the baking schedules would have to be organised so that batches due for baking in succession would require similar oven temperatures and the mixes would have to be ready at the right time.

    2. Tom 7 Silver badge

      Re: Can someone explain

      Lyons tea rooms were ubiquitous. Almost every town in England had at least one. The guys running LEO managed to write code to do stock control, logistics and calculating staff pay and tax on a machine less powerful than a modern keyboard controller. For several years LEO worked out takings, tax, wages, refilling stock requirements and deliveries. 12 or so people ran the computer and had ERP worked out far more efficiently that several hundred Oracle consultants 30 years later and for astronomically smaller money.

      1. bombastic bob Silver badge
        Happy

        Re: Can someone explain

        accounting, M.R.P., inventory control, and orders+deliveries.

        The heart of business computing. They were pioneers.

        1. W.S.Gosset Silver badge

          Re: Can someone explain

          And all in PoundsShillings&Pence -- no decimals!

        2. Tom 7 Silver badge

          Re: Can someone explain

          Also they knew what they were trying to program. I find actually understanding the problem makes the coding faster and better. As I got more experienced in coding I discovered that almost everything people try to do in business has already been emulated in code too and often better than businesses try to implement it. The pleasure in writing functioning code that does what a customer needs rather than what they asked for is often matched by the look of pleasure in the customers when you casually demonstrate something 'I thought you might like to take a look at this as I think it may help cover your requirements'. Alas some people would rather you did what they asked even if it wouldnt work,

          1. W.S.Gosset Silver badge

            Re: Can someone explain

            You would not believe the push back I got from senior mgt every time I pushed to get even key developers out on client sites so they could see how the system was used in practice. (Which is transformative for complex systems in complex situations.)

    3. david 12

      Re: Can someone explain

      The term used more often in the original memos is "Bakery sales and valuation"

      http://www.computinghistory.org.uk/det/66297/P1-3-Bakery-Sales-Valuations-Perforating-and-checking-current-data/

      The job is working out the value of bakery sales, which I guess must be used for planning bakery lines.

      And they same to have had different bakeries (locations?) for different lines. I remember when bakeries in Australia were consolidated from one in each state: evidently there was a previous round of consolidation.

    4. SW10

      Re: Can someone explain

      Some context, perhaps…

      A few years ago I was at a family gathering and got chatting to an old guy and discovered we had both worked in the same building in the City of London.

      As he explained his job to me I was aghast to realise that he and perhaps hundreds of colleagues were simply human calculators.

      The big shots upstairs would request a calculation, which would then be sent down to be worked on, using what sounded like drafting boards from his description

      1. John Brown (no body) Silver badge

        Re: Can someone explain

        "As he explained his job to me I was aghast to realise that he and perhaps hundreds of colleagues were simply human calculators."

        His job title was probably "computer". Yes, that word was a job title before it got re-used for the meaning we now use today.

        1. Neil Barnes Silver badge

          Re: Can someone explain

          c.f. the Manhattan Project: https://ladailypost.com/manhattan-project-women-calculators-paved-way-for-modern-computers/

        2. hayzoos

          Re: Can someone explain

          This reminded me of a story from one of my computer science professors. He had the opportunity to meet a computer professional from the USSR. The gentleman claimed the title of compiler. He actually manually compiled some higher level computer language to machine language.

    5. the spectacularly refined chap Silver badge

      Re: Can someone explain

      From vague memories of the Georgina Ferry book already mentioned in this discussion, it took a list of what had been produced and calculated the inputs required (ingredients, fuel etc) and coated those along with the value of the products made. It was chosen as the first job because it was reasonably self contained, and not overly time critical (it was what we would now call MI) in case of breakdown. They dared not start using it for payroll until they had a second machine. It also didn't require large amounts of I/O. It was here that Leo made it's biggest contribution: previous applications had essentially been compute intensive so I/O was not a major consideration.

      Most envisioned tasks for Leo were the opposite: read a record, do a few basic calculations, output the result, read next record... Developing those I/O facilities took time.

  14. Anonymous Coward
    Anonymous Coward

    About the same time....

    An uncle of mine (no longer with us) was doing an engineering apprenticeship at Rolls Royce (the aero bit, I think, not the car bit) in the mid 50's. His night school classes were full of log tables and slide-rules, but his teachers, both at RR and college were always talking about "The Computer". He recalls a busful of apprentices setting off one dawn morning for a day out to see "The Computer" somewhere (he couldn't recall where - Crewe?, Derby?) and them all gawping at the behemoth of a machine the size of two tennis courts humming and whirring away. He also recalls everyones bewilderment as one of the operators got it to print out a set of log tables or do some mind-boggling calculation in just a few seconds or tens of seconds. The operators were keen to say that there were folks who believed that one day every factory or design office could have one of these machine to help with tedious calculations.

    As a RR apprentice he also managed to save enough money, along with one of his brothers to be able to rent a TV set and have it installed at my grans house in time for the '53 coronation. My mum remembers they were the only family on the street to have TV and all the neighbours coming round. Indeed I think she was the only girl in her class at school with one.

    He lived long enough to see battery operated computers held in the palm of a hand, which had integrated wireless telephones, video cameras, music players, pinpoint mapping systems and access to a worldwide database of mankinds knowledge.

    Somehow, I doubt we will see such leaps of technology in such a short time again.

    1. John Brown (no body) Silver badge
      Thumb Up

      Re: About the same time....

      My grandad remembered seeing the news headline here in the UK of the first powered flight by the Wright brothers. He also watched the Moon landing, live, and had a flight on Concorde. I wonder which of the new inventions we have seen will be the "Concorde" of our dotage. Especially those young whippersnappers who are reading here.

      At the very least, most of us have seen the birth of the Internet, the WWW, wireless comms, smartphones etc.

      1. Neil Barnes Silver badge

        Re: About the same time....

        My grandad also: he was born before the Wright brothers flew, and he lived to see walking on the moon become so boring they stopped showing it live on TV. Though I don't think he ever flew, and certainly not on Concorde.

        When I started working (as I think I've said elsewhere) my engineering training at the BBC included both calculating gm curves for thermionic valves and a single lecture on the microprocessor (the 8080 was released a couple of years before i started working); I maintained and repaired valve audio equipment - tape machines, record players (sorry, BBC, reproduction players!), and amplifiers - and a few years later mentored colleagues through these new-fangled microprocessor thingies.

        I watched audio go from analogue (including equalisation of the contribution circuits) to digital point-to-point circuits to IP and video do essentially the same, from analogue to digital to HD. In 1999 I knew *every* piece of equipment in World Service that contained a computer or processor - from tape machines to comms equipment to HP-UX mainframes and which of them would be affected by Y2K - the HP mainframes were the biggest culprit, they needed replacing. In 2009 or so I and two colleagues converted the BBC's analogue and digital communications backbone to a new fast digital infrastructure...

        I am basically an expert on obsolete technologies. Truly, we live in an age of wonder.

        1. Tom 7 Silver badge

          Re: About the same time....

          My granddad was engineer on the R33. My bro recently found hand written instructions for servicing its engines - at least one of which is in storage somewhere. He was convinced H2 could be used in airships safely in the 60s and that you could make airships that would carry passengers in comfort to the US in under a day cheaper than airlines could then.

          I do wonder if now we could try the same now - the fuel savings are potentially enormous - especially as the can be covered in PV and run entirely CO2 free.

  15. Phones Sheridan Bronze badge

    Was Lyons Electronic Office a backronym? I always thought that it was an astrology pun.

  16. cantankerous swineherd

    "fizz of excitement when a bit of code does what it should" - the awesome "stone me, it works" moments are what still keeps me futzing with machinery that sort of mostly performs according to my conception of what the specification means.

  17. Plest Bronze badge

    Claim to fame

    My nan was one of the first few woman to be a manager of a Lyon's Corner Tea House, women were usually employed as "Nippys" the waitresses, but the managers were always men. My nan has long since since passed on but just one of those wonderful family things that makes me proud that feminism wasn't something that started in the 1960s.

    1. Tom 7 Silver badge

      Re: Claim to fame

      I had a next door neighbour who was an extremely good early coder for IBM who should probably have been hailed but being female wasn't. Alas she developed Alzheimer's before I could get her story down.

  18. anthonyhegedus

    But can it run... oh, never mind, I'll get my coat!

    1. herman Silver badge

      Can I get a Leowulf cluster.

  19. Anonymous South African Coward Silver badge

    Memory lane

    LEO is older than myself, but it is good to see what the pioneers used back then.

    And it is interesting.

    Big (and old) iron still have a certain attraction and still looks good after all these years.

    1. Spoobistle

      Re: Memory lane

      Also fascinating to read about the way hardware and software were optimised to squeeze the most out of the available technology. Rather different to the current attitude of "throw more GHz and more GB at it".

  20. captain veg Silver badge

    on a roll

    "that very first business program, designed for bakery valuation jobs"

    Batch jobs, presumably.

    -A.

    1. herman Silver badge

      Re: on a roll

      Bugs and mice must have been very unwelcome.

  21. rogbrady

    Leo- Minerva Road

    Leo 3 and Leo3F (Leo326) werw developed and built at Minerva Road,Park Royal London - I worked there in 1962/63. It is nor often mentionedthet Leo 3 was the only computer in Western Worfd that could be openly exported to the Eastern Bloc at the height of the Cold War as it had no military significance. In fact I remember my suoervisor telling me to sort out the logic of a magnetic tape controller as it was going to,Czechslovakia. I didn't belive him but did as I was told! Years later I found that it was true.

    Leo 3 used diode/resistor logic and had a multitude of circuit board types, while 3F had only a few. 3F was ahead of its time,but limted because of circuit path lengths limiting its processing speed.

    1. Lars Silver badge
      Happy

      Re: Leo- Minerva Road

      Nothing against your claims about the Leo 3 in 1962/63 but seriously it was all about IBM also in the Soviet Union.

      " ... ("Unified System of Electronic Computers") was a series of clones of IBM's System/360 and System/370 mainframes, released in the Comecon countries under the initiative of the Soviet Union since the 1960s. Production continued until 1998. The total number of ES EVM mainframes produced was more than 15,000. ".

      https://en.wikipedia.org/wiki/ES_EVM

      And for the history:

      https://en.wikipedia.org/wiki/History_of_computing_in_the_Soviet_Union

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