LEO editor

Stan Evans, Maintenance Engineer on LEO I and LEO II, joined LEO 1956

Date of Birth:  Born  23/09/26

I never realised that my life was about to dramatically change when l went to Joe Lyons at Cadby Hall in 1956. for an interview for a job as maintenance engineer working on their first computer they had ever made.     I was an experienced electronic technician but knew nothing about computer digital technology.

I was interviewed by the computer engineering manager Peter Mann. He asked me many questions but sadly I did not do very well with my answers. To my surprise and pleasure he offered me a job. It later emerged that all the other candidates had the same lack of knowledge that I had.

What was unique about this computer was that it was the first computer “worldwide” that was designed to do commercial type work. The other computers in use were basically scientific machines.

 Lyons formed a company called LEO Computers so in fact I joined this company not Lyons.

There were two other chaps who joined me the same day. Les Rabitt and Stan Holwell.     Now this is where I go for a wobble trying to remember names. However here goes.

The senior engineers already on site. Frank Walker, Jimmy Wheeler, George Manley and a much older chap Chas.  These were the chaps who not only had to mend LEO I but had to teach us rookies.

Although there were detailed schematics of every specific unit in the machine there were no written notes on the logic. ie how the computer worked other than the hand written notes of our tutors . I pause a minute to reflect “You cannot get more basic than that.”

Our work shop was a 12 ft by 12 ft  room located across the corridor from the Computer Room. In addition to us engineers there were three other people in this room.

To help fixing computer faults every unit type had a spare unit. I think they were called LCU xx If a fault was traced to specific unit and the fault cleared when replaced by the spare then Hey Ho back to the operators and the machine was up again. In the work shop the faulty unit was put into the Test Rack.

This Test Rack had simulated features to be able to test the unit and find the fault. There was a very clever engineer called  Gibson. He maintained this test rack and also was involved in the thinking about the next step LEO  II. Also in the workshop were two ladies.

One was a very experienced lady who did all the electric wiring in the units (modifications etc) The other lady was a thermionic valve tester. She had a check list of units that had been operational for a certain time period and checked all the valves and if below the Makers specification replaced them with a new valve.

The huge irony was that a development engineer chap called Lenearts  established that new valves were more likely to fail than the comfortable settled in old ones. So this testing of valves did not really do any good. So this procedure was stopped.  We were learning all the time.

There were two people we often worked with on the computer. They were David Caminer and Mary  Blood. They were in fact the first Business Computer Systems and Programmers in the country and David led a small team of programmers who had written all the LEO I operational jobs since 1952 which was quite impressive.

Programmes were written in machine code format and stored in the main memory. This consisted of a number of special long tubes filled with mercury. They were stored under the false floor together with a number of smaller tubes, registers that contained only one word of 17 binary bits.  Note. I am struggling here and hope I have got it right. I would think the main memory had 32 tanks and each tank 32 words.

I seem to recall a D30 digit. Perhaps that was Leo II

 Basically a line of machine code had 4 areas. Each area had a specific significant meaning. If the programmer wanted this action to be an ADD he would put a number in binary in the first area because he knew that number told the computer to ADD. The other three areas were locations of the two numbers in the action and where the answer was to go. Clearly this format would not be the same for other instructions.

How about that a programme lecture in one paragraph. The point of this paragraph was to illustrate how basic the programming was.   Cobol, Fortran etc  was not even a dream in these days. 

Mr Caminers  team had written several programmes which tested the performance of the machine. When it failed we were given the reason. If it did not fail we used the margins tester. We had over a 1000 wires from the engineers control panel going to the most crucial electronic sections in the machine. These wires sent electronic signals that increased or decreased digital pulse size. Use of variation of threshold often made the performance test programme fail. Using eliminating switches It was a simple matter to find what unit was causing the programme to fail. 

In certain difficult faults Mr Caminer was a great help in typing in a simple programme which clearly showed what action was going wrong, the engineers were then able to get moving with the oscilloscopes and find the fault.

I have enclosed a picture of a young engineer all 30 years old Stan Evans himself working at the LEO I engineers control desk. It was here that the engineers and Mr Caminer did our fault diagnostic work. Very often the engineers would do the same for the same reason. A small loop of a failing instruction made oscilloscope work easier.  

Interesting to note that the Operators rarely use the engineers panel because at that time operations control was done using Punch Cards. These cards had been successfully used for many years for basic business tasks. They were 3 inches by 7 inches, had numbered columns 1 to 80 with rows numbered 0 to 9. Rectangular holes were punched out in each column.

To start a programme the operator would push a button called BOOT which placed into the computer Order Tank an instruction to read a card into the computer. This card contained the necessary instructions to read the complete pack of cards into the computer. These cards contained sequence of computer instructions ie the programme, and the scheduled commercial programmes was then ready to run. The operators area was dominated by three big heavy card readers, equally heavy printers and a paper tape reader.

The inevitable happened of course the work load had got very heavy so we had to go to three shifts. I hated the night shifts and I think in hindsight we would have preferred One week of nights and two weeks day/evening. However we three new chaps were very rapidly promoted to Shift Leaders because the senior chaps were moved to Minerva Road factory where work on the next generation computer LEO II was moving very rapidly. Oddly enough I cannot remember anything about our junior engineers at that time.

Doing nights did have one advantage and it’s a story I was very fond of telling. The Lyons management who were very highly regarded and so were provided with an “Out of this world” restaurant. Two lady chefs looked after the restaurant at night. I used to chat these ladies up. Most of us, the engineers and operators enjoyed a very basic level of living so a full roast and three veg was a real treat. I was often offered if it was available a Dover Sole. I have never seen such a big Sole since then. A quarter of an inch fish each side of the bone and the fish overlapping the plate. This is how the rich or talented lived. I missed that!!!! when I eventually moved from LEO I So back to the real story.   

Very soon the first prototype LEO II was completed and installed in a different but near bye building to Cadby Hall. Both Les and Stan had moved to Minerva Road but in spite of my pleading I was still left in charge of LEO I. Something about good training in Management for me. Eventually LEO II / I was up and operational taking the commercial work off LEO I.

Transfer at last. No training course slot available so straight in as Shift Leader with new trained engineer Tony Talmadge
to help me. (no the name is not right ) I knew LEO I so well that the experience was invaluable when thrust onto LEO II and Tony was good. Hurrah.

  The concept was almost the same but the electronic engineering had taken a massive jump forward. Not only was the machine considerably faster it now had magnetic tape which meant good bye to loading programmes and storing data on clumsy punch cards. Delay mercury tubes were still used for the memories. So given time and not too many nasty faults I soon settled in to my new job.

 However even then it was “Stan they are in trouble on LEO. I can you go and help them”!!  I suppose I took it as a compliment.

I was on LEO II / I for about 18 months when I was asked if I would be willing to move to East London and install a computer LEO.II/9. Consult with family and Yes. I was also able to help commission the machine at Minerva Road with a chap called Peter Ross before taking it out and installing it at Ilford (the photo people). In the following years we became good friends but that is a Honeywell story.

What was unique about LEO II/9 was that the main memory .was now stored in a new device called a Core Memory instead of bulky mercury tubes.

I was now living quite close to Ilford which made a marvellous change not having to travel a long distance to get to work. I soon settled down and with a good crew I had very low down time.

I should have realised with my past LEO career it would not last for long. My friend Stan Holwell had been made Area Manager and I was asked to take up the appointment of Area Supervisor to support him and in particular address myself to problems at LEO II / 5 the in-house LEO machine located in Hartree House London.

There was a piece of new peripheral equipment being installed called  Magnetic Drum but with good support from Minerva Road that ceased to be major problem and it soon became fully operation.

This was a Random Access Device (RAD) that enabled a programme to zoom in very quickly for data instead of a long wait going along a magnetic tape. Disc Drives did not arrive on the LEO II’s

Leo II’s were all thermionic valve machines with the inevitable problem of long periods of down time There was still quite a few difficult faults on Leo II / 5 that required me motoring from Ilford to mend them(Always late evening)But it was always satisfying to fix the problem and get back home again.   

Reading back my report its interesting to note that the our memories are very selective. I read the Leo Computer Society members list and see that there were many chaps who I worked with and many others who sadly may have gone now who I do not remember.

One thing I do know Leo produced some of the most highly competent, dedicated engineers and regarded as the best in the country. 

My career path with LEO finished quite abruptly for Honeywell Controls advertised for engineers to start up a Computer Division. These computers were the equivalent of the LEO III’s No valves fully transistorised. My golly what a nice change.

So after five years very exciting time with LEO I left and installed the first computer Honeywell had sold Bournemouth Town Hall. But that is another story.    

To finish my Saga there was a humorous story about LEO II/9.

Many years later all the LEO II were being replaced with LEO.III’s Fully transistor techniques replacing the unreliable thermionic valves. The machines had little value to the Scrap Merchants except for all the mercury in the old memory tubes. One such dealer thought he had bought LEO II/9 for a song! When his gang arrived to remove the machine he found to his horror NO MERCURY it had a core memory.  See also version with photos at https://docs.google.com/document/d/1EjtC3VTgqRgZ2HZGUwB4D9gbd2gcUNmm2aPHgMwmMME/edit  and at https://www.dropbox.com/s/im70jnacidwe2jq/Stan%20Evans%20LEO%20Maintenance%20Engineer.docx?dl=0

Stan Evans Review of John Daines Zoom forum presentation on 14^th July 2021 and reminiscence of TRT in action:
John Daines was brilliant . Not only the very professional way he gave the presentation but the many items of news I did not know. In particular those related to TRT in the war. Also Lyons  running successfully a war effort factory.
One memory of TRT was in the middle of a nasty engineering  fault on Leo I he came down and quite rightly wanted to know our progress. We had been down 3 hours by then.
He suggested you go into the work shop , have a cup of tea,switch off for 5 mins then recap the problem 
Needless to say it worked. we were up  again in 20 mins. A lesson I used many many times later on in my career
So I repeat John gave a brilliant presentation.
Of course feeding my ego he points an arrow at your truly at the Leo I engineers control  desk in the section Maintenance 

Professor Stephen Evans   I was interviewed by John Pinkerton prior to my graduating from Keele University in 1966.  I was offered by Dr Pinkerton, sponsorship to do a PhD in any subject in any University that I wished (it’s possible I still have that letter but can’t put my hand on it now).I didn’t want to do a PhD then, as I had had 3 years in the sixth from at school (I did my A levels at age 16), followed by going to Keele for 4 years and having a scholarship to go to Swarthmore College, Pennsylvania for a year, so I had already had 6 years in academia post my A levels- I wanted a job. I started work the week after graduating from Keele in the Research Division at Minerva Road. English Electric-Leo had just had “Marconi” added to the name and I worked for John Winterbottom on speech recognition and visual display design. With Ann Cropper I published a paper in 1968 on “Ergonomics of Computer Display DesignThis seems to have gone on being cited up to last year.
[https://scholar.google.co.uk/scholar?cluster=3718501728846242519&hl=en&as_sdt=2005&sciodt=0,5&as_ylo=2014]
       I don’t know whether some reminisces of working at Minerva Road in the Research Division would be of interest- it was obviously post Leo, though I did learn CLEO and Intercode. I left EELM to go to CERN in 1968, and worked as a programmer there for Carlo Rubbia, subsequently a Nobel Laureate.
       I changed the focus of my career several times and I am now semi-retired and paid to work 1 day per week at The London School of Hygiene & Tropical Medicine.
       I recall various people from 1966-68 in addition to Pinkerton and Winterbottom. Ernest Lenaerts was around Minerva Road then; I did meet you very briefly and various other luminaries of the time but I’m sure you won’t remember me. Ann Cropper and I were involved in the start of the British Computer Society “Display group”, and our paper was based on a talk I gave in one of the early meetings of that group.

Mike Finlay      Memories of LEO              
I was born in on 18^th April 1937  a true Londoner within the sounds of Bow Bell, did my National Service between 1955 and 1957 at the RAF Air Radar School as an RAF Radar Theory instructor, and then studied at Jesus College, Cambridge for the Natural Science Tripos Part 1, followed by the Economics Tripos Part2, graduating in 1960.

I joined LEO after Cambridge. The Careers Advice fellow at Cambridge said that my Natural Science and Economics degree together with my Electronics experience in the RAF suggested I should try for a job in the nascent Business Computer industry, so I had interviews with ICT, IBM, NCR, and LEO. LEO was the standout option, due to the recruitment process whereby we were given a lesson on some basic machine coding and then set a problem to solve by writing a program. This gave an insight into what the job would entail, unlike the others which were basically a simple form of IQ test.

I did receive offers from all four – though the non-LEO ones were for punch card processing rather than computing. It was an easy choice, and I joined LEO in September 1960, as a trainee sales consultant. My first task was to rewrite a payroll data vet program for Tate and Lyle on the LEO II/1 bureau at Cadby Hall, though I was based at Hartree House. The rewrite was necessary as the program’s many modifications had made it too big for II/1’s massive storage capacity of 2,000 words – ie 1K bytes!! Happily, the rewrite was a success, and I learned the value of constructing a comprehensive set of test data to ensure the program could cope with all eventualities.

I then moved into Frank Land’s Consultancy team, under Mike Jackson, to work on the Renold Chains project. I remember the concern of their management team about this new-fangled idea – “Will we still be able to make chain?” was a frequent query at progress meetings!

I learned how to write Job Plans the LEO way, with flow charts etc, and the value of studying what the client needed to be done, as opposed to a “One system fits all” approach to tendering and project implementation. I also enjoyed analysing the LEO III sort program, in order to produce a ready reckoner for calculating how long the sort would take for different input variables.

I worked on many interesting projects under Mike and, later, John Aris and Doug Comish. These included Post Office Premium Bonds, Stewart and Lloyds, Shell Mex BP, Manchester Corporation, HM Dockyards and many other Government Departments. I remember our contacts at the Treasury were a Mr Alcock and a Mr Balls, which I hope did not represent the government’s views on our efforts. There was also a memorable two weeks in Prague at the Communist bloc Computer Exhibition in 1966, on the EE-LEO stand under Ralph Land, and it is good to see both Frank and Ralph at the LEO reunions.

My visits to Shell-Mex BP being driven by Mr Caminer, and to Renold Chains in Manchester in Mike Jackson’s Austin Healey Sprite, were particularly memorable if rather hair-raising. It was always good to arrive!

I shared an office at Hartree House with Ninian Eadie and Mike Gifford, both of whom had stellar careers  LEO, and I also met LEO II Chief Programmer Susan Finch, my wife now for 55 years and counting.
As LEO III activity increased, and later System 4, I became Defence Sales Manager under John, but I fear without much success, and my last post before the ICL merger was as Government Sales Dept Systems Manager. ICL then made me Regional Systems Manager South for Doug Comish’s Local Government Sales Division, which meant working at an old ICT office in Beckenham. This was a two-hour commute, so when a Computer Systems Manager job came up in Cockfosters, 5 minutes from my house, I left ICL in autumn 1969 and began the second phase of my career, which ended as Director of Strategic Planning for TSB Retail Bank Division.

I retired in 1992, and my best memories are the early days at Hartree House, working alongside fellow graduates and professionals, doing a job both innovative and exciting, whilst also enjoying a vibrant social life with some colleague or other throwing a party nearly every weekend. LEO was truly a ground-breaking project, and I am very proud to have been involved. When people ask me “What did you do?” on the golf course, I always tell them about LEO and what it meant for the future of British business management.

https://www.dropbox.com/s/ye54m4sfqwkh1fz/Mike%20Finlay%20Biography.docx?dl=0

John Fletcher, I was a maintenance engineer for approximately 20 months on the Leo 3 at British Steel site Ravenscraig Motherwell in the late 60’s.   I was employed by English Electric Computers at that time who also serviced the process control computers in the strip mill.  Our Leo training took place at the Post Office Edinburgh site.  Great training and experience as I remember.  a good foundation for the rest of my computer industry career. I remember the Leo has been fairly reliable and therefore not needing much attention.  Spent more time with the document reading/paper tape generating data processing data..  Christchurch Dorset is now home.  .Tel.  01202 255870  mobile 0748 838 4414

John Simon Florentin, Computer Operator            I used to work on Leo III’s at Shell Mex’s computer centre in Hemel in about 1965-67. I thought I had better write something about this before I disappear for good.
         They had two of these machines that were to us exactly the same.  All this was on the lowest level of the building where it crossed the bottom end of Marlowes in the centre of Hemel-Hempstead. This building has since been replaced.
These machines were run 24 hours a day Monday to Fridays. There would be two teams of about 4 operators on each shift, one for each machine. The only other persons around on the night shift would be someone in charge of the whole shift, the cook to feed us and a person who was the magnetic tape librarian and the engineers. On the night shift the operators would be fed at about 12.00 at night and the computers would be handed over to the engineers who would do whatever maintenance was necessary. They frequently did not use there allocation of time and it was possible for anyone who wanted to, to run their own programs.  I think one machine was handed over to the engineer for an hour then the other for an hour. When the operators were not working or eating one popular pastime was playing cribbage. On the end of the week night shift there would be a very large sort that took most of the shift. But when it finished everyone went home early.

Each machine had eight tape drives (no discs) These would be four on two channels –  so the source files would be read in from two drives on one channel and output to two other drives on the other channel. The source file would be on about 10 tapes.

This meant that one person would be working almost by himself juggling these tapes all night. On top of this, every now and then the tapes containing the current partially sorted file would be saved just in case a re-run was needed. During a large sort like this the machine could run up to two other programs 

All programs had to be typed onto paper tape and then read in.

I think the words in the memory were 48 bits long. One or two of these were parity bits as operators would get SPF’s on the console denoting a store parity failure.

      It was said these machines had a floating point option fitted.

The control store was in a box about 1ft cube. Inside was a three dimensional array of fine wires with very small cores at what appeared to be random points.

The paper tape reader was made by Elliot but the paper tape punch was made by Teletype. The printer was made by Anelex. There was also a card punch and reader. There might have been a reader for reading forms where boxes were selected by drawing a line through them (Editor: Lector or Autolector). The whole machine was made using transistors except in the tape drives, TM2’s made by Ampex.  Thyratrons were used to control the roller used to press the tape against the drive. The density of the bits on the mag tape was such that we had a gadget with a sort of fluid magnetic liquid in it such that individual bits could be seen.

https://www.dropbox.com/s/qwhc24ztw05iyab/John%20Florentin%20memoir.docx?dl=0

John Forbes,    Reminiscences.     Joined Leo in early 1960. Did a few ‘odd jobs’ for Leo ll.  In summer was told that I was to lead a small team writing an Intercode Translator for Leo lll. My immediate questions were, “What is Intercode?” “What is a Translator?”  With a small team created Intercode translator
Working closely with Master routine (MR) had Translator and its MR interface working in 1961.

Moved to CLEO compiler in 1962 with a larger team.

      In 1963 on spent more time accompanying consultants to answer/explain to prospects how Leo software worked.

In 1964 IBM announced 360. Moved to team designing ‘new range’.  Abandonment of ‘new range’, after ‘deal’ with RCA for Spectra series.  Worked on System 4 and software support until moving to Canada in 1969

              Two points raised I think I can provide comments on.

1. Why CLEO rather than COBOL?  This will go down in the annals of LEO history as one of the great internal debates. (I was not party to it).In the red corner we had the proponents of CLEO (Clear Language for Expressing Orders) It was a clearer language than COBOL. It sought to combine the facilities of COBOL AND FORTRAN in the requirements it addressed. And perhaps most importantly it was the brainchild of TRT. In the blue corner we had the proponents of COBOL led by DTC. It was an already accepted high level language. This meant that it would be easier for a company that had COBOL programs to convert from another machine to a LEO machine. (Far-sighted in that uniform tape standards, programming languages had not yet emerged as a long-term goal).

Anyway the RED corner won by a KO and I was instructed to produce a CLEO compiler, for which I was given a somewhat larger team than had been the case with INTERCODE.

2. Why did the CLEO compiler produce output that was input for the Intercode translator?

In the initial design stage, the objective was to produce object code ready for handling by the Master Program in the same format as the Intercode Translator; and we had experience of doing this. Inside the team there had been little if any discussion about whether that was the right way to go. Then came the suggestion (from Mike Josephs, I think) that we should go the Intercode route. The argument for going this way was that the CLEO compiler would be ready sooner, both because it would cut down on some of the work that had to be done in earlier passes of the program and because some additional passes would not be required. The argument against was simply that each compile would take longer.  I agreed with the Intercode route, on the understanding that we would later be able to amend the compiler to be expanded to incorporate  the translator functions. (Of course, this never happened and many members of the team and I were long gone into other roles soon after the Intercode version was working.)

3. High level languages v low level languages and computer road blocks.  The pros and cons of this debate have been well versed for many years. What, even now I believe as I swear at my laptop, is an understanding of what is the critical component that slows down the execution of a program. For many years it was the speed of the cpu. In one organisation I became familiar with a critical long running batch program ran every night. The solution was to get faster tape drives. Surprise! the run time of the critical update program did not decrease.

Now I look at my lap top and wonder why a program takes so long to load or a file to be found. The disc drive has (in my case) become the limiting factor. My experience is that very few installations take the time to analyse where their road blocks are.  See https://www.dropbox.com/s/qhekzhfa8jh4lwb/John%20Forbes%20memoir.doc?dl=0

I was dozing on the settee when I became aware of LEO on the screen and Wendy Craig uttering the words Lyons Electronic Office.  Bill Forfar: Reminiscence – Article – Computing History

• Wendy Forward Memoir by her daughter Anna C Page

My mother, Wendy Elizabeth Forward, was a computer programmer during the early 1960s in London before embarking upon overseas travel She read mathematics at Reading University, and graduated from there in July 1963 (her degree certificate says ‘Pure Mathematics, Applied Mathematics and Geography, resulting in a BSc Honours 3^rd class). She was a programmer on the Leo III business computer from approximately September 1963 until about August 1966. The Leo was the first business computer in the world, invented during the early 1950s for the Lyons Teahouses (Leo stood for Lyons Electronic Office). See: http://www.leo-computers.org.uk/newphotos.htm for photos of Leo I, Leo II and Leo III. My mother worked in the Lyons main bureau computer at Hartree House, Queensway, London http://www.leo-computers.org.uk and there are some wonderful photos of the installation of this machine – by crane through the window! This machine was in use from 1962 – 1972.

My mother lived near to the computer, in Leinster Square, and then later she moved to Fitzjohn’s Avenue in Hampstead. I succeeded, via the Leo Computers Society, to get in touch with one of her former colleagues who confirmed that she had been a Leo programmer. Her colleague, Peter Byford, told me “We all had a great time at Leo although we worked long hours. We all got on well, your Mum was a nice lady, good programmer, sometimes worried more than most when things went wrong but an important part of our programming team. She would have worked on CLEO and intercede” (programming languages).

My mother’s first dog in Cape Town was called Cleopatra was a Great Dane, the runt of the litter (Cleo for short). We had always thought that Mum had named her for the Egyptian Queen (though we didn’t know why), however CLEO stands for ‘Clear Language for Expressing Orders’ and was the plain English programming language developed for Leo computers (but which ultimately lost out to other programming languages – see pages 164-165 ‘A Computer called Leo’, by Georgina Ferry). To me this just shows Mum’s quiet and ironical sense of humour that she named her dog after the programming language she used, especially as dogs are (hopefully) controlled by commands.

Leo Computers merged with English Electric in February 1963, in October 1964 EE bought out Lyon’s holdings and the computer company was renamed English Electric LEO Marconi, in 1967 it merged with ICT to form International Computing Limited (ICL). These first two events would have taken place while my mother worked for the company. ICL later lost out to IBM and the USA market and then the Japanese has predominated the computing world ever since.

I remember my mother’s reaction to the first Apple home computer that friends of ours acquired in the early 1980s. She so wanted a reason to justify the expense of acquiring one, but despite the fact that it could have helped with the household accounts, the accounts for her mathematics coaching and the weekly letters to her parents and sister, she resisted the urge to buy one as she saw it as a luxury and was very careful about saving money. I so wish that she had bought one, though she would not have had long to enjoy getting to grips with programming again because of her early death.

My mother was an inspiration to me in so many ways, although I only had her for 13 3/4 years. She would have been pleased with my achievements at the Open University (both as a student and member of staff), as I am proud of hers at Leo: what a great technology role model to have in my family.

Wendy and Cleo, 1968.  See also  https://www.dropbox.com/scl/fi/md6e105079om96rvzjaw7/Wendy-Forward-by-Anna-Page.docx?dl=0&rlkey=ykq9u1x4qen2f36p2l9st9ydz

Nigel Furness, I was involved in 1981 in decommissioning the Bristol machine, LEO III-70 which was a 326 model (editor: the last LEO).  Prior to decommissioning I had been employed as a systems engineer to provide engineering support for this machine.  I had been trained at Charles House which was a BT (formerly GPO) installation, as was Bristol and Cardiff.  I was unaware that the guys who were training me had been at the forefront of computer science in the 1950s.  Many of the concepts embodied in LEO are to be found in today’s PCs – multi-channel DMA for example, though LEO’s version of a DMA controller was called an “assembler” – a term guaranteed to cause confusion in conversation with programmers.  LEO III had the world’s first multitasking operating system, called rather quaintly “the master routine”.  It also had a microprogrammed CPU – a very advanced idea at the time.   LEO was beautifully made and all those engineers who worked on LEO were very proud to have been connected with the machine and we were very sad when we switched it off for the last time.  I and (I think) six other colleagues were the last generation of engineers recruited by ICL to work on LEO and I joined the company last of all, several weeks after the others in January 1980.  I have to say that much of what I learned during this period has underpinned my entire understanding of computers and it was a marvelous opportunity for a young engineer to have experienced what some have called “the golden age of computing”

•  

•