Who can explain the Turing Machine?

CanonDjango

CanonDjango

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CJ
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i just watched The Imatation Game which was fantastic. But it left me wanting to understand exactly how turings machine worked.

I read some web pages and I watched some YouTube vids about it but I'm totally confused. I'd love it if someone with a good knowledge can explain it.

Here is what I know and understand

1 it works on tape
2. The tape has cells
3. Each cell contains a 1 or a 0 or a space
4. The machine sees the symbol and decides to leave it, change it or store it then moves left or right

Some questions

1. How does the machine see the symbol? Is it using a lens? How does it know what the symbol is?
2. How does it change the symbols? Is it ink that is erased and redrawn?
3. How does it make a decision to move left or right or leave or change? It doesn't have a microchip so how does it actually do an if logic action?

I have more questions.
 
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I haven't seen the film (I should), but did study the Turing machine around 25 years ago. The Turing machine was envisaged as a hypothetical rather than physical device so:

1. How does the machine see the symbol? Is it using a lens? How does it know what the symbol is?
Doesn't matter, it just does.

2. How does it change the symbols? Is it ink that is erased and redrawn?
Doesn't matter, it just does.

3. How does it make a decision to move left or right or leave or change? It doesn't have a microchip so how does it actually do an if logic action?
The instruction table tells it what to do given the content of the state register and the value on the tape in the current location. The mechanism by which that is achieved does not matter. The way the instruction table is stored does not matter.
 
Why are you saying those things do not matter?

Those are the things I want to know how they work.

I'm talking about the actual machine he built to crack the code. It was a physical machine that's what I want to know how it worked
 
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All I know is that Turing probably contributed more to the war effort than any other single person and was treated like sh*t afterwards.
He should have been knighted and acclaimed as one of our greatest. Instead he was imprisoned in 1952 and then died two years later.
 
There is a book by Hugh Sebag-Montefiore called Enigma. It's all about how the codes were cracked.
There is one chapter and a series of appendices all about how the bombes and banburismus worked. Very clever stuff - I think. It's way above my salary grade so I skip that bit. If you understand such stuff the book is definitely worth a read.
 
For some reason I get a blank, black square when I try to look at my first image so I don't know which one you are referring to. If you post a link to it back here I will see if I can work out what it is.

EDIT: I can see it now. It's part of Colossus.

There were several types of machine used to crack the codes. Most of them purely mechanical. Somewhere on my page is a video of the Bombe machine which used multiple rotating hubs, each fitted with three sets of 26 way contacts which connected with wire brushes. I think the idea was to run through the code looking for closest matches to known sequences of words.

The pictures of the larger machine with valves was the Colossus computer. In the same building was a machine which I didn't photograph unfortunately. It was mechanical, using telephone exchange type uniselectors and a teletype machine.
This machine would run through two reels of punched tape simultaneously looking for likely matches depending on entered set up codes (the teletype code for the text was punched into the tape). It did this at a fairly high speed so that when it found one, it would stop and reverse back to the position where it was found. Once the whole reel had been check, it was rewound and the test was done again but stepped by one character. This was continued quite a few times.

I don't understand all of the maths and logic involved but the electronics and mechanical aspects are understandable. The principles are fairly basic but the complexity is in the scale of it. i.e. keeping one set of rotating contacts going reliably is o.k. (think about Scalextric car brushes) but when you have 78 pairs (I think) on one hub and there are dozens of hubs, the maintenace must have been continuous.

I am always much more impressed with mechanical solutions to problems as they usually show much more ingenuity than today's method of just connecting up a microprocessor and programming it.

Obviously in the 1940s they did what they could with what they had - and in their case, a modern (or even a 1970s) computer would have made the task much easier.
 
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So when it stopped working, and the user rang up Turing, did he just tell them to turn it off, unplug, and turn back on again?
 
I have recently been reading a few books about Bletchley Park/Station X and Alan Turing.

How the Enigma code was cracked is most interesting. The machine had a weakness that helped. It's security depended on rotor wiring and that remained unchanged from the 1920's until 1945. Also, no letter could be used to replicate itself in the code, because the electric circuit could not be made if that were tried.
Operator error was another factor. Some operators always used the same header when composing a message and a weather report was also sent.

http://crypto.stackexchange.com/que...the-original-ww2-enigma-machine-from-a-modern

That is quite an informative website.
 
Trust me if you want to try to understand it go to Bletchley Park and see the rebuilt Colossus, it is an amazing feat of design even today.

Go on the tour of park as they take you around all the various parts and also to see Colossus, where they give a quite good and fairly easy to understand description of how it works. My parents house is only about 20 minutes away from the park so I've been a good few times and I still think there's that I've not been to yet; the tickets that you get are also valid for up to 6 months (or it might be 12) so you can go several times without having to pay again (although there is a separate fee to visit the National Computer Museum on site - trust me though it's worth it).
 
s162216 said:
the tickets that you get are also valid for up to 6 months (or it might be 12) so you can go several times without having to pay again
Click to expand...

That's why we are planning to go again.

One of the staff told us that last summer they had a visitor from Belgium who was staying in the area for two weeks - and he came to the park every day!

s162216 said:
(although there is a separate fee to visit the National Computer Museum on site - trust me though it's worth it).
Click to expand...

Definitely. Although most of the computer museum was closed when we got there but the Colossus room was open and admission to that was just £1 each.


Steve.
 
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Steve Smith said:
That's why we are planning to go again.

One of the staff told us that last summer they had a visitor from Belgium who was staying in the area for two weeks - and he came to the park every day!



Definitely. Although most of the computer museum was closed when we got there but the Colossus room was open and admission to that was just £1 each.


Steve.
Click to expand...

To go into the actual main Computer Museum is a few pounds each (which is only valid once) as it's technically a separate entity to the rest of Bletchley Park, but it is well worth it as the great majority of the equipment they have works and it's fun/educational to use computers which are in some cases twice (or more) as old as me! They actually had an Amstrad PPC640 exactly like the one my Dad saved from being thrown out at work and gave to me - that was a prominent feature of my desk for quite a few years (described as portable computer... which is true as my dad did actually used to transport one all over the place for use in his job as a field engineer).

Another place to go in the park is the museum of cinema - they have working cinema cameras and projection equipment from all eras, and even a small screening room where they project old newreels etc throughout the day.
 
CanonDjango said:
Why are you saying those things do not matter?

Those are the things I want to know how they work.

I'm talking about the actual machine he built to crack the code. It was a physical machine that's what I want to know how it worked
Click to expand...

The machines that cracked the codes were the Bombe (an electro-mechanical device for Engima, designed by Turing) and Colossus (a valve based electronic computer, designed by Tommy Flowers, for the Lorenz cipher).

You asked about a Turing machine, a hypothetical device he envisaged well before the outbreak of war which has a formal definition for modelling computation theory and is not intended as a physical device or for code breaking. I answered about it.

Bletchley is well worth a visit, particularly to see the recreated Colossus IMO.
 
onomatopoeia said:
The machines that cracked the codes were the Bombe (an electro-mechanical device for Engima, designed by Turing) and Colossus (a valve based electronic computer, designed by Tommy Flowers, for the Lorenz cipher).

You asked about a Turing machine, a hypothetical device he envisaged well before the outbreak of war which has a formal definition for modelling computation theory and is not intended as a physical device or for code breaking. I answered about it.

Bletchley is well worth a visit, particularly to see the recreated Colossus IMO.
Click to expand...

indeed it is clear from the thread that I thought the machine that broke to code was called a turing machine, but was corrected in post number 6

do you know how the bombe machine or the collosus actually work? Like how do they physically work to crack a code - I need to read the link above
 
My old boss helped rebuild the bombe. proper mad professor type he was, so I wasn't surprised.
 
archstanton said:
Hi CJ, try this:
http://en.wikipedia.org/wiki/Cryptanalysis_of_the_Lorenz_cipher

Unfortunately there's no short-cut explanation as it's bloody complicated! You have to read it :)
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gosh that is tricky

ok I watched this video and now I understand how the enigma machine itself worked


so i'm using that to assume that the bombe was setup to find out what combination of settings were needed that day to turn the word "hskldmn" into "weather" or "jkliet" into the word "hitler"

they new which word was going to say weather or hitler and they could see the pattern so I'm guessing that the bombe went through permutations of settings constnatly until it matched the words they needed. How it actually physcially did that - I don't know but I will continue to try and understand it
 
CanonDjango said:
gosh that is tricky

ok I watched this video and now I understand how the enigma machine itself worked
Click to expand...

That is about as good a demo/explanation of the machine as I have seen. Got to admire the quality of the engineering. Notice the electrical contacts on the rotors. Just like those on a lens mount.
 
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