HP Forum Archive 21

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OT: EDSAC simulator Message #1 Posted by Mike (Stgt) on 19 Aug 2013, 9:27 a.m. It is not new and what it simulates is very old: the Edsac simulator, simulating the "electronic delay storage automatic calculator" of late 1940. Why do I mention it? There comes a 'Sieve of Eratosthenes' program with it which visualises the sieve process. For me it was an eureka! Ciao.....Mike

Re: OT: EDSAC simulator Message #2 Posted by Tony Duell on 20 Aug 2013, 4:25 a.m., in response to message #1 by Mike (Stgt) Quote: It is not new and what it simulates is very old: the Edsac simulator, simulating the "electronic delay storage automatic calculator" of late 1940. Why do I mention it? There comes a 'Sieve of Eratosthenes' program with it which visualises the sieve process. For me it was an eureka! Ciao.....Mike I was told (by Professor Maurice Wilkes himself) that one of the first programs run on the original EDSAC produced a table of squares (I think by adding up successive odd numbers). This did not impress people as squaring was not hard to do on a (much simpler) analogue machine. The next (?) program produced a table of primes, I guess this Sieve of Eratosthenes. This caused considerable interest as this was something that could not be done on an analogue machine and showed that EDSAC could do something new.

Re: OT: EDSAC simulator Message #3 Posted by Mike (Stgt) on 20 Aug 2013, 7:27 a.m., in response to message #2 by Tony Duell Eratosthenes is not new, EDSAC is quite old (first kind of RISC?) but for me it was new to _see_ how the Sieve of Eratosthenes works. And this experience was so "Whow!" I allowed me this OT append. This sieve process is an excellent example to show the difference between calculate and compute: with very little effort you 'find' the next prime like picking ripe fruits from a tree. After the 2 you get the 3 as only integer between 2 and 4 = 2^2, with the 3 you know all primes between 3 and 3^2=9, with the 5 you know all primes up to 5^2=25 and so on. And this insight I _saw_ the first time with the Edsac simulator. :) Ciao.....Mike

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