welcome back around the same time that John Mockley was creating eniac for the US Army another computer was being built in Bletchley Park England was also in the middle of course of World War II just like Conrad zoo was doing his thing in Berlin you had people at the US Army but also in England Building computer and it reminds us that war mobilizes science ever since Leonardo d venci uh signed up to work for the warlord Caesar boura at around 1500 you can go throughout history and see how each new war or military need helps create new forms of technology one of the interesting things about World War II though is that it wasn't just new weapon systems it was computers that became crucial to the war effort and what happened was in Bletchley Park the British government gathered a group of mathematicians and thinkers and all sorts of brilliant people with the goal of breaking the German wartime code the Germans were encrypting their messages and of course if uh they could be intercepted Ed and then decoded that would give the Allies Britain in the United States and its allies a great advantage and so they recruited people for this wartime effort by many little test one of which was how well you could solve the crossword puzzle in the Daily Telegraph in England and they called it colonel Ridley's shooting party so that the people in the town of B Bletchley didn't quite know why these people were coming or going Bletchley is a small town and its main advantage for this was that it's halfway between Oxford University and Cambridge University on the rail line now the point was to take what was known as the German Enigma coding machines that's what you see on the screen and the Germans would encode their messages by typing them in and there will rotaries that would move back and forth so that each of the letters would be encrypted and every time they did a new message they changed the encryption on uh the Enigma machines that made it very hard to break the British got a lucky lucky uh break when the pole some polar soldiers captured one of the uh encryption machines for enigma and for a while that was working but the Germans caught on and they made it more phisticated they added more rotors and so you needed some brilliant mathematicians to help figure it out the most brilliant of them of all was Alan T we're going to hear a lot about him later we're going to talk about his question of whether machines could think but Alan touring first became famous by going to Bletchley Park and helping to create the machines that would break the German code when I wrote the innovators I was looking forward to making uh touring a little bit more famous I thought people hadn't heard of them and they really should but just as I was publishing the book Benedict Cumberbatch played touring in a movie called The imitation game which you should by the way go see or uh see on uh download it because it's really good about bedley Park and how they broke the German Enigma code and so bened Cumberbatch ended up making touring more famous I didn't need to do it but touring uh to me is some body who represents the essence of figuring out the birth of the digital revolution in 1936 right when Claude Shannon is doing his master's degree thesis on how you would do logic in circuits with onoff switches toring wrote a paper called uncomputable numbers and he did it because he was trying to solve one of those great mathematics Ral riddles of the time it was one of uh it was a riddle or a question question about some mathematical uh theories are unsolvable or some mathematical equations are unsolvable there's some problems that we just haven't been able to solve and the question was is there a way to figure out when you have a mathematical question whether or not it's solvable uh to know to be able to distinguish between those that are going to be solvable and those that we're never going to solve touring did it by inventing in his head with thought experiment a conceptual machine that would do logical sequences and you would figure out from that whether or not a theory was solvable or not don't worry about the mathematical question of solving uh this uh dilemma of unsolvable equation just remember the universal Computing machine which which is the thought experiment touring had and came up with and he said it's impossible to invent a single machine that can be used to compute any computable sequence once again like Shannon this is exactly 100 years after adal love lace is talking about creating machine that can do any computable sequence not just math but anything that can be notated in logic and finally uh you have Alan Turing coming up with this concept of how you would design a universal Computing machine that could solve any problem or show that the problem was not solvable and so what he did was he at Bletchley Park created a machine called the bomb b oom be and what it did was it was able to take the German code compare messages and quickly see if you could decode it and after a while he had two operating bombs there was a problem the Germans pretty much figured out that some of their messages must be getting decrypted and so what they did is they comp they completed an even more complicated machine and it took a new form of computer to try to break it that's a guy named Tommy flowers on your left and he worked in some called Hut 11 at Bletchley Park there's Hut 11 it's on the grounds of Bletchley Park Tommy flowers was an expert at using vacuum tubes radio tubes those things I told you that we you were use in eniac look like old inesc light bulbs and what he does is he creates a machine that uses vacuum team tubes just like John Vincent at a Nassau had used a few of them at Iowa State University and certainly eniac was using them at pen and they were able to store the German messages in memory and then compare them against a paper tape of new memories and by December 1943 the people at Bletchley Park led by Tommy flowers Alan touring and a guy named Max Newman were able in December 43 to create what was known as Colossus you see a picture of it there 1, 500 vacuum tubes and soon by June 1944 right near as the war was uh in its last year they created a version with 2,400 uh tubes and that version just as it came online in June 1944 did perhaps the most important single thing in winning World War II in the European theater and that was it broke the messages of the German military right before D-Day before Eisenhower lands in Normandy uh with dday and it made sure that the Germans were confused and were not preparing for a Normandy Landing uh before so that means that before eniac which was November 1945 the British had a fully electronic and digital computer in fact it was binary used onoff switches but unlike eniac which had 10 times the number of tubes Colossus was a special purpose machine it was designed only to break the German codes it couldn't do missile trajectories it couldn't do atom bomb explosions all the other things so it was not what we call touring complete meaning it could do any computable sequence or to put it another way it was not like adal lel's dream of a general purpose computer which leads us to question who invented the first computer and that of course depends like most questions on how you define something like how do you define a computer and we don't really want to say an abacus is a computer or that an adding machine is computer so we can look at the early people in the early 1940s who worked on computers George stibitz there in the upper left and Howard aen next to him conr zoos in his lab in Berlin John adof at Iowa State Allan touring uh uh Tommy flowers out at Bletchley Park they all invented some form of the modern computer but for me I would Define a computer I would say here's the necessary ingredients a computer has to have this is just me other people can argue what was the first computer and to me to be a computer the way we Define it today what we mean when we say computer is it's got to be digital in fact not just digital which can use any numbers like one through 10 or something but binary on off switches yes no doing it in circuits with switches that turn or vacuum tubes that turn on and off so it's got to be digital and binary it's got to be to my mind electronic using mechanical switch is that's not if you saw something like that you wouldn't say that's the modern computer and to me just like ad love L says it has to be general purpose so the winner is to me eniac and there you have press record on the left John Mockley Jean bark and others at the University of Pennsylvania doing what I would call the world's first uh computer a binary digital electronic general purpose computer thanks