Colossus & Other Early Computers

The Colossus, EDSAC and Harwell Dekatron (WITCH) were some of the first electronic computers. In this video I check them out at the National Museum of Computing, along with an ICL 2966 mainframe from the 1980s.
This video was produced with the kind cooperation of the National Museum of Computing, who checked the script for factual accuracy. The museum is located at Bletchley Park in the UK, with its website at: www.tnmoc.org/
Note that my intertitle which says "Harwell Dekatron (WHICH)" contains a typo -- it should say "Harwell Dekatron (WITCH)". Sorry about this. :(
My second report from the National Museum of Computing -- looking at early PCs -- is here: • Early PCs at the Natio...
If you enjoy these videos, you may also like my coverage of some early laptop and mobile computers:
Toshiba 5100: • Classic PC: Toshiba T5100
Atari Portfolio: • Classic PC: Atari Port...
Apple Newton Messagepad: • Classic PC: Newton Mes...
Psion 7: • Classic PC: Psion 7
More videos on computing-related topics can be found at: / explainingcomputers
You may also like my ExplainingTheFuture channel at: / explainingthefuture

[@stuartthegrant]

So glad you gave Tommy Flowers the credit for building Colossus. A most interesting look at the history of computers in the UK.

[@cyrfung]

This channel feels like the 80's technology shows I watched back then. I absolutely love it.

[@GamingHistorySource]

Hard to believe that we carry computers in our pockets now that are over a million times more powerful than these old machines. Interesting video ! I really enjoyed this. :)

[@elimalinsky7069]

The microcontroller in a modern coffeemaker is at least a million times more powerful than the EDSAC. Now that is impressive!

[@ronaldmcdonald8303]

Now were talking about quantum computing, their thousands of times more powerful then todays super computers, Instead of several atoms making up 1 switch, a single atom can do up 2000 calculations. Quantum computing is the future of both computing and AI!!! Were even now using DNA to store information and nano technology is progressing quickly. The future will be a very different place from now.

[@vgamesx1]

7:46 "200MB of storage" Damn, who could possibly use that much storage? Nobody will ever need more than 50MB.

[@ExplainingComputers]

:)

[@encycl07pedia-]

It's still hard for me to believe average consumers will use a 1PB internal drive, but based on history, it's not improbable. Then again, I wonder if/when the compression technologies will stifle or at least slow the growing storage trend.

[@HappyBeezerStudios]

I went from 160 GiB to 7 TiB in only 10 years. Which is about a 30 times increase. Even if my demnnd for more memory slows down dramatically over time, I guess I would reach that 1000 TB Threshold withing the next 30 years

[@kallewirsch2263]

160GiB? The year I joined the university for studying Informatics (1982) , operators would have killed for that much memory space! That is, after they were brought back to life from faint. A 4MB IBM/360 managed all the computing needs of the whole university :-)

[@paradoxzee6834]

I remerber in 2004ish on my computer class when my teacher say that in few years we might see 1TB hard drives and it sounded far fetched to me because at the time stores usually sold PC's with a 40gb hard drive. Heck I remerber thinking that a PC does not need more than a 80gb hard drive.

[@Screamingtut]

I worked at DEC Digital Equipment Corp back in 1978 -1981 then from 1983-1985 I first started to work on hard drives similar to the one's on the ILC system but they were made by CDC Control Data Corp. they were 200-300 MB 20 heads (two for each platter one platters was a servo signal to keep all the data heads aligned.

[@tuforu4]

I Started in 1979 as technician , its amazing how i still remebver so much , the 7400 series was every where back then.

[@markfrombriz]

I started my career as a VMS sysadmin, DEC had a great OS and solid engineering. Sad to see their decline

[@zboy303]

Enjoyable video, thanks. Would love to see more historic computing episodes, covering the 70s, 80s and 90s!

[@ExplainingComputers]

My second video from the National Museum of Computing (on early PCs) will post in July. If this video and that one prove popular, there will be more! :)

[@ExplainingComputers]

I have a playlist of some of my "classic hardware 80s and 90s) here: kzbin.info/aero/PL2m2YvnrOYxLaMqqr95ToBdPAeRTyAJ_m

[@david486038]

Yes, your videos on these subjects are very well presented and informative. Thank you so much for taking the time.

[@zboy303]

Thanks Chris. Naturally, I've already watched that playlist :)

[@TheTOBroShow]

You never fail at giving viewers interesting angles on computers.

[@vgamesx1]

It is quite amusing though, how a computer only 60-70 years ago could easily fill an entire room, whereas today we have tiny little boards the size of a couple fingers such as the Pi Zero which cost about $10 and still has insanely more processing power, while only consuming as little as 5 watts, it may not be the scifi world people dream of but it's still pretty amazing sometimes.

[@ExplainingComputers]

I agree. Given where we came from, where we are now with computing IS amazing. And when you think how far we've come in a relatively short time, it is exciting to think what lies ahead . . .

[@pikachu5647]

vgamesx1 😳

[@powder-phun949]

Try to imagine a face of a 50s enginieer, who was just told, that in the 2000 the machine he operates will fit in a square milimeter, and cost less than $0,1

[@robpasley2517]

When I went to see the ICL they said they had put all the disks onto a micro SD so that they could run the thing without having to put the aircon unit on.

[@robpasley2517]

At the time Tarmac was using this I worked for another construction company who used an IBM RS6000 based machine the size of a fridge freezer. I was using Progress 4GL which had little trouble with 2 digit dates.

[@southsidedojo2]

Man, words can't explain how much I really liked this. Thank you Chris for the education you share with the world and I really hope you never get burned out. Cheers

[@ExplainingComputers]

Thanks.

[@emph66]

Very interesting, love seeing these ancestors to the modern computers. The fact that Bletchley Park is still being used as a museum is a surprise and what better place to display these great machines.

[@cdl0]

Many thanks for showing us around TNMOC, CB@EC! The nice thing about the very early computers is that they are constructed from a few hundred conceptually simple units including logic gates, shift registers, adders, a clock, some sort of memory, and so on, which implement maybe a dozen instructions, making it possible, with a little effort, to understand exactly how they work. Thus, although they are quite simple things, these primitive computers appear to be almost miraculous thinking machines, simply because they can perform repetitive operations, tirelessly, at rates significantly greater than a human being is able to do.

[@reggiep75]

I wish I had a single purpose computer that would press the like button every time for me. I love these vids and it reminds me of old 80's BBC school documentaries that were highly interesting back in the days gone by!

[@hondacxrider]

I bought at auction a box full of old valves, a few of these were MOD stamped and red. Just the types of valves colossus used, and I was able to donate them to the late Tony Sale to help his rebuild. I actually met him and a really nice guy.

[@ExplainingComputers]

Cool.

[@hydraADL]

I visited this museum on my recent trip to Europe, all the way from Australia. I have so many good memories of these computers. thanks for uploading.

[@timnichols3823]

One of my uncles worked on an ENIAC computer in the day. He was excited when he got a commodore 64. He unfortunately passed away in the early 80's but he would have loved to see computers of today!

[@ExplainingComputers]

I bet he would be amazed at how far the "descendants" of ENIAC have advanced.

[@MicrobyteAlan]

Happy Christmas, I'm just having a nostalgic day, and searching for old computers. Look what popped up. Thanks, very well presented.

[@ExplainingComputers]

Happy Christmas! :)

[@kolkoki]

One of the most interesting video on KZbin at the time. computer history is fascinating.

[@joshpayne4015]

I had the pleasure of visiting the National Museum of Computing and Bletchley Park last month. An incredible place!

[@inisipisTV]

Simply wonderful. Good to see you getting out of that green screen and into the real world showing us the wonderful and fascinating history of computers.

[@Bp1033]

I love computing history. It really just brings it back into perspective that these little black boxes we keep in our pocket are truly an amazing accomplishment.

[@booboyBL]

Thanks for this. I will have to visit Bletchley again soon. The last time I visited was about 10 years ago, and I can see a lot has changed.

[@ExplainingComputers]

There is so much cool stuff at the museum (which now runs independently of Bletchley Park).

[@DimusTech]

That's an amazing video! I read in the past about few of those computers and it was really fascinating to see some of them "alive" in your video! Please do more of those videos of looking in the past, it is really interesting and your explanations are very good.

[@iVaporizeHD]

What a fantastic video Chris! Thoroughly enjoyed watching it - I think I'll have to visit and see them all! Thank You!

[@Wenslock]

When I watch your videos, I often get a feeling of nostalgia. Your shows remind me of the shows from the 80s and early 90s. I love it. :) Keep up the good work!

[@leewmlee]

The ICL 2966 brought back fond memories of school. my friends and I spent many many happy hours mucking around on it before pcs were widely available. to get around the time limit quota assigned to each student, after spending a few hrs on a session, we used to login concurrently from another terminal, logout from the original terminal, then logout out from the newly logged in terminal. the newly logged out terminal overwrote the time usage of the earlier session. we were careful to make sure that our usage was about 80-90% of our weekly quota to avert suspicions.

[@SyphistPrime]

I love these old computers. It shows the humble beginnings we've really come from. I love seeing what challenges were overcome with things like core memory being destructive read, and the use of more mechanical parts.

[@BernardColdwell]

This takes me back a while, great to see the old machines, the ICL was a very popular machine in its day. Having worked for many many years with those hard disks and tape systems its a long way from the mini and modern computers today. Thanks for sharing

[@lucatrifan2797]

These videos on location are really nice, I hope you will do more of them in the future, maybe have some guests or other computer KZbinrs from the UK.

[@ExplainingComputers]

Thanks -- very useful feedback. :)

[@CAHSR2020]

This video was great. Very enjoyable and I'd like to see more like this. That being said, please resist the temptation to add guests and collaborators to a solo channel. I've watched this happen a hundred times and it never ends up anywhere near as good as you'd hope. In fact they're often some of the lowest rated/watched episodes in the entire catalog. Better that you visit a channel that is built around giving interviews instead. People who already know your channel can learn more about you and you can introduce yourself to a much larger audience who have never met you. Just my opinion though. :-)

[@cee128d]

Especially nice for people like me who would more than likely never be able to visit them in person. Travelling across the pond from the USA is just not a viable option of many of us.

[@pikachu5647]

luca ioan guesting someone as calm and composed as him would be good, but guesting the flashy mkbhd/Morrison etc would ruin the soothing and calm experience,

[@mr.nathanneil88]

Wow, this is such a fascinating video. The punched paper tape is so intelligent, love it!

[@hasansalim1868]

Hi Chris. Thanks for this "traveling to the past" episode. Very nice.

[@oldmanhuppiedos]

I can still remember the first computers. The developments have not stopped.

[@risvegliato]

Wow! My dad was a lecturer at Wolverhampton Polytechnic in the 70's and I remember seeing the WITCH. So glad its been saved.

[@ExplainingComputers]

This is great to hear. A fantastic connection.

[@quincy1048]

Love the video quality on these old machines nice work

[@alavena]

Been there a couple years ago. It was an extraordinary experience. Lots of things to see and activities for kids as well. A whole day well spent.

[@TiborRoussou]

Thank you for your time to make and upload this video; really well done! :)

[@realmchat6665]

Another great video, thank you for the quick tour. I look forward to the video on the smaller machines. If you are looking for ideas for future videos, please consider doing more in-depth historical pieces on some of the machines you covered in this video, I find these histories fascinating. Thanks once again for all of the excellent content that you produce.

[@craigjovanovich6450]

Can't wait for the PC videos! Great video!

[@b_mb4948]

Great to see you out and about "on location" Chris! Top-notch content as always!

[@ExplainingComputers]

Thanks.

[@TheCatLady65]

Holy shit, now I feel old! I used to work on the 2966 when I was a young engineer at ICL back in the eighties :) Now it's in a museum, hehe.

[@ExplainingComputers]

Time catches up on all of us. I'm just editing the follow-up video today on early PCs, and I cannot believe old some of these "recent" pieces of technology now are!

[@TheCatLady65]

Wonderful, can't wait to watch it! I must say, even though I feel a certain nostalgia seeing these old computers, I'm more than happy to embrace the latest technologies.

[@spikekent]

Chris, you give us such a diverse rage of material, and every bit is enthralling. I have been meaning to visit Bletchley Park for a long time, I didn't realise TNMOC was on the same site ... Like I needed more incentive :-) Got a week off next month so hope to make the trip then.

[@wdhewson]

Good one. Thanks. More history please.

[@Bluez2008]

Great show looking forward to seeing more

[@joeschmo2693]

Very interesting. Computing history is fascinating - I'll watch and like any such video you post.

[@ExplainingComputers]

Thanks! :)

[@1MrPooney]

Love the channel. Your style is deff unique on youtube. Good job.

[@ExplainingComputers]

Thanks.

[@devinemichae]

Excellent video, you are very good at explaining things. Keep up the good work!

[@dennissmithjr.5370]

Wow professor, this was a great video today. Loved it and can't wait for next ones.

[@ExplainingComputers]

Thanks. I was not sure what reaction this would get -- my first ExplainingComputers location report!

[@TheColinputer]

Awesome video! I remember seeing some early photos of the EDSAC build while back. Looks to of come along nicely.

[@whitenorthstar]

Great bit of history...thanks for sharing it with us!

[@DavoidJohnson]

Bletchley Park was also the place where I and many other telecoms technicians received our early training from BT. So hello to any of you who are still kicking around

[@ExplainingComputers]

Excellent! :) And I think there are indeed several more of you commenting here.

[@rtesimpson]

Great stuff Chris...can't wait for the next one!...

[@ronbee5299]

One of the Best early Computing docos ive seen. ThankYou Awesome

[@TheWraithkrown]

Awesome video. It is a bit awe inspiring how far we have come in 70 years.

[@thewatcher5271]

Hello Again & Thank You So Much For Sending This Link. I Have Several Documentaries About Bletchley Park During The War But You Make It & Post War Advances Even More Interesting. This Made Me Reminisce About My "First", A Tandy RL-1000 With Two, Low-Density (720K) Floppy Drives, No Hard Drive & 512K RAM. A Hayes Compatible 2400 Baud Modem Was Used To Dial-Up Local BBS & To "Expose" My Nostalgia, I Still Have The Copy Of Telix I Used On The Flash Drive I Keep In My Pocket. I Shan't Bore You Any Longer & You Sir, Will Never Bore Me! Thanks Again!

[@ExplainingComputers]

Thanks for watching, and I'm glad you liked the video.

[@wb5rue]

Excellent video! I've been in computers for 40 years but I learned quite a bit from this video. I was surprised at how early "computers" were in operation. I'm also impressed that the reconstructed machines are made with more or less original components -- I'm amazed that the components can be found.

[@ExplainingComputers]

I asked about this -- they apparently use "new old stock" -- 50 to 40 year old valves that have never been out of their packaging, held in storage by the origonal users of such machines.

[@jaime57473]

Love your work mate. Awesome!

[@ExplainingComputers]

Thanks.

[@StephenFarthing]

I wrote code for and managed ICL1903a, 2966 and Series 39 machines. We used them for stock control, payroll and some more esoteric stuff such as radio frequency prediction. At the time I could program in COBOL, S3 which ICL programmed much of VME in. There was a Fortran compiler and an Algol 60 compiler for both the 1900 and 2900 series systems. I also implemented some systems on an ICL DRS 20 system, which was one of the first networked 8 bit microprocessor systems ( unusually I think ICL bought the design in and badge engineered it, the mainframes and associated operating systems were done in house) . I guess this was in about 1985. They were still running payroll and personnel for about 200,000 people back in the 1990s. It's quite interesting to consider how little computational power and storage mainframes had but how much work they could get through. And how efficiently one had to code to get a program to fit in say 4 megabytes of memory. It's quite ironic really because now I program microcontrollers for fun and pretty much all of them have more power and memory than I ever had on a mainframe. Just out of interest I need some blank punch paper tape. Does anyone know of a source?

[@scyther1141]

Hyped for the next video!

[@eukat3ch]

Thanks for the video Chris, very nice.

Great information on history of computing. The parking lot resembles the scenes from the movie "Enigma".

[@dj_paultuk7052]

Great place. Been there 3 times now. The ICL is very similar to the Honeywell DPS6 that i used to operate in the late 80's.

[@JeffAdairKTM530]

Thank you for doing these videos - Amazing work. God speed

[@DeannaAllison]

I really enjoyed watching this - thanks for your excellent and interesting video!

[@ExplainingComputers]

Thanks! :)

[@NeilRoy]

One of the first computers ever made used no electricity at all, but was completely mechanical. Due to constant breakdowns, the inventor later replaced the mechanical parts with some relay switches. It's a fascinating topic.

[@MichaelFlood-ho8kd]

Just watched a KZbin video on Colossus hosted by the national museum of computing by Chris Shore ( recommended) and stumbled on your video. Another goody, thanks.

[@MikeNHOC]

That was pretty awesome! Thank you so much for sharing!

[@XSpImmaLion]

Great stuff Chris! Some of the hardware later in the video I had the opportunity to see as a child in operation where my dad worked... fond memories. xD My dad was an engineer for a contractor company of the Itaipu dam here in Brazil, but before myself coming into existence, he had already worked with valves, punch cards and whatnot. He used to teach classes later in his career so he had samples of the stuff... very unfortunately lost in between moving from one place to another. The oldest PC stuff I still have is probably some floppy disks. I remember that the job place he had into the computer department was an entire building where half of it was the refrigerated server room, and the rest of the building were offices with dumb terminals built litteraly inside desks (custom made desks with a monitor and keyboard built in). They still used floppy disks of the 8 inch size. The server room had a whole bunch of wardrobe sized units, some with spinning taperolls, some for other purposes. The room was refrigerated 24/7, floor had these thick cardboard-like perforated tiles with all the cables running under it. But the thing I remember the most is the printer. It was pretty huge for a child me. xD It opened up like a fridge, and had it's own vacuum cleaner to suck up the bits of paper that came off that perforated paper used for dot matrix printers. All very fascinating.

[@ExplainingComputers]

These sound like wonderful memories of early and large computing! Thanks for sharing.

[@The_Last_Post]

Great video! I visited Bletchley Park and the then joined National Computer Museum back in 2010, now I believe it's a separate entity. Great to see the place again and really like this style of video Chris, can't wait for part two. oh and more of the same please! :)

[@ExplainingComputers]

Thanks for your kind and positive feedback! I was not sure what the reaction to this video would be -- it is something different for the channel. The National Museum of Computing is indeed now run separately to the rest of Bletchley Park.

[@Bearthedancingman]

You make a better documentary than History Channel. I'd listen to you teaching computer history for hours if I could. It's so interesting.

[@ExplainingComputers]

Thanks.

[@S-I-T]

Thank you for an excellent video.

[@medworthy]

+ExplainingComputers / Christopher Congratulations on creating an interesting and historically accurate video. Looking forward to your reviews of old computers.

[@ExplainingComputers]

Thanks Mark.

[@DreQueary]

Thank you so much for this video. You are doing great work. I really appreciate it.

[@recyclerlemur2129]

I been learning alot from your videos keep up the good work

[@ExplainingComputers]

Thanks. :)

[@Willibef]

Looking forward to the second part.

[@genericgreensquid6669]

Awesome video! I love old computers!

[@evil_in_your_closet]

Very cool video Chris! Really fascinating to see how it all started and came to be... I found the ICL Mainframe to be most interesting and had to smile when i spotted the C64 (my personal "digital origin") and the Commodore PET in the shelves. If you keep going with this kind of subjects, i would love to see a video dedicated to the CRAY machines and its vector processor!

[@ExplainingComputers]

Thanks for this. They have half a Cray at the Museum . ..

[@evil_in_your_closet]

OOOOH Fancy!!! I went to a (german) Computer science Museum once, because i heard they had an XMP there... never seen one before, so i kept looking... couldn't find it... so i sat down on what looked like a fancy red bench and ate my sandwich... then one of the museums guards told me to please not have lunch on the Cray XMP xD I would love to learn more about the vector processing and how it works, possibly even about the cray history.... Those things are amazing! I even found a working Cray Emulator on the net ;-)

[@ubaidq34]

Excellent work. Thank you Sir.

[@mikeyoung9810]

Love the history of computers. Good video.

[@CindyBradyTooh]

OUTSTANDING video! VERY interesting!!! I look forward to your next one on older PCs. ~Cindy! :)

[@ExplainingComputers]

Thanks. :)

[@MrCataV]

This reminded me how old is may laptop... now i want a new one. Thank you. Let the online shopping begin :)

[@stevedoubleu99B]

Nice video, reminds us where our wonderful little devices all began.

[@jimmychapman9964]

This was like what PBS used to be, love this stuff!

[@chrisyboy53]

Fantastic video thoroughly enjoyed watching every minute, will defo make a visit to that museum. Keeps those KZbin videos coming.

[@ExplainingComputers]

Thanks! :)

[@scottharrison6061]

Awesome. I was at the museum on the 4th June. Fantastic display

[@ExplainingComputers]

You were there three days after me! :) The second video, shot in the PC Gallery, uploads this Sunday. :)

[@leenob]

Great videos. As a software developer /coder, I find the history of computing incredibly interesting. I released the game called "Charlie the Chav" on the android play store, which I based on old 2d platform games of the 80's. I did it for fun. However, it was done in Java, using very simplistic techniques of OOP that you had no way of getting around, back then. In the old days, you had to code for so many problematic hardware restrictions, such as the type of display unit, the memory, and lack of colour. You had to be very clever, and almost use bodging techniques to accomplish your goal. Now, it's so easy to produce anything. Even a child can develop software. But, what I like to see is this kind of content. We are back to the roots and the guts of our modern cpu. Every bit of hardware we use today comes from this equipment in some way. It should be worshipped. Pure geniuses created this technology.

[@ExplainingComputers]

Great post -- I could not agree more about getting back to the "roots and guts of the modern CPU". A great line! :)

[@maicod]

In The Netherlands in the late 80s or early 90s as a son visiting my fathers job I visited a building called Coengebouw property of a Dutch Bank and it had similar computers and those large cased disc stacks and machines to drive them as the ones of the ICL 2966

[@antonioeblen6662]

Great video as usual ! I remember my first computers the wonderful ZX81, Timex-Sinclair Spectrum, Commodore 64. They were the actual population computer beginning. Thanks

[@ExplainingComputers]

All of these machines -- and more -- will appear in the follow-up video sometime in July. :)

[@TheRantingCabbie]

The EDSAC had a memory of 3KB. You'd almost have to look back and laugh knowing that's not even a config file these days. When we look back at storage capacity in the 90's, it wasn't that much. I resurrected a Win 95 Aptiva with Win 98SE not long ago. But what I found strange was it had a 4 Gig HD. Back then you'd expect 1.2 Gig at the most.

[@NickFellows]

Loved this , more where this came from please :)

[@niallwood]

Very interesting, never knew that computers were so different back then!

[@AlarusOne]

Excellent and amazing!

[@ejyanezpvideo]

You left me eager for more...! txs!!! :)

[@ExplainingComputers]

More soon . . .

[@joeyb4ever]

I find tubes (valves) endlessly fascinating. I build high end audio with them, and have built many scratch projects, a few using what are modern computer type tubes.

[@xSuperManW3x]

My mind is blown!!!!! That someone actually made something like those early PC's....... Modern PC's aside... how could ppl come up with that... just WOW!!!!!

[@ExplainingComputers]

Thanks for this. I too am amazed at what the early computing pioneers achieved, and how our hardware today evolved from their amazing work.

[@McRocket]

Incredible stuff.

[@supergoofy123]

Just two words: Thank you

[@perrymcclusky4695]

Looking forward to when you cover more on this topic.

[@mCKENIC]

Fascinating! Thank you!

[@grahammccarthy1893]

Ha - I did my apprenticeship on the prototype ICL 2966 (codename S3) when I worked at West Gorton in Manchester between 1976 and 1980, I helped design one of the boards in the OCP. The very first one went into the Inland Revenue in Dalkeith I recall. Never could get the 64 bit (N64) version working though. Those were good days.

[@dupre7416]

I spent a good portion of my early career programming the IBM AS/400 mainframe in a language known as RPG. I worked on successors to the AS/400 until 2012 at which point I was unceremoniously laid off. I had to completely reboot my career. I am now an app developer working in much more modern languages. I do sometimes long for the simpler days when there where only a few hundred commands to remember. But overall, I'm probably having more fun.

[@MarcellDAvis1103]

Very great and professional video.👍

[@ExplainingComputers]

Thanks. :)

[@simonbeasley989]

Brilliant, I'll definitely have to pay a visit to the place.