Hi Victor, > anyone who has not used Google today and who is interested in Turingia > might like tyo see that they have honoured his centenary with a Turing > Machine-inspired (I assume) Google Doodle .
A bit of background on it. http://www.google.com/doodles/alan-turings-100th-birthday > I have to confess I do not quite understand how it works... I don't > know if there is a second level puzzle where you have to reverse > engineer the TM ;-) I don't know of a way of playing it past its date? It had two rounds of puzzles. On each go you have to alter the presented machine, some parts are fixed, others in colour can be cycled through the allowed options, to generated the target sequence of 0s and 1s from the starting sequence. When you hit play the machine is run and the result is compared digit by digit. If you are successfully another letter of "G o o g l e" becomes coloured in. Colouring all six letters completes the round. The target sequences are the Baudot (ITA2) code of the current letter to light, e.g. O is 00011 IIRC. On getting to the end the icon that shows whether the digit being checked matched or not, = or ≠, changes to what looks like a rabbit. It is a rabbit and clicking it shows a more complex machine that when run churns out a famous sequence. Here's a picture of a more complex program in it. http://sbf5.com/~cduan/technical/turing/turing-1.png The machine itself has a tape with squares. Each square can be either blank or have a 0 or 1. One square is the current one under the "reader". The "instructions" in their program let one overwrite the square with a blank, 0, or 1, move the tape left or right one square, and test if the square is blank, 0 or 1. It also lets you jump back several steps in the program to do those instructions again. Execution proceeds left to right unless a conditional instruction has one move down a row. So that program shown starts 1 -- write a 1 1↓ -- if we're over a 1 move down a row X -- erase, e.g. write a blank → -- move "reader" right, i.e. tape left ␣↓ -- if we're over a blank move down a row oo↺ -- step back two instructions The last three make a loop that hunts rightwards for a blank. Cheers, Ralph. -- Next meeting: Bournemouth, Tuesday 2012-06-12 20:00 Meets, Mailing list, IRC, LinkedIn, ... http://dorset.lug.org.uk/ New thread on mailing list: mailto:[email protected] How to Report Bugs Effectively: http://goo.gl/4Xue
