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<!--replace-end-7--><!--replace-end-4--><!--replace-end-1--></head><body><div class="ui fluid container universe"><!--replace-start-2--><!--replace-start-3--><!--replace-start-6--><div class="ui text container" id="zettel-container" style="position: relative"><div class="zettel-view"><article class="ui raised attached segment zettel-content"><div class="pandoc"><h1 id="title-h1">Turing Machines</h1><h2 id="what-is-a-turing-machine">What is a Turing Machine?</h2><p>Turing Machine is a machine that contains mutable state, executes sequences of simple instructions that read and write that state, and can pick different execution paths depending on the state (via conditional branch instructions.)</p><p>This is a general expression, it is typically expanded as follows.</p><p>The machine consists of an infinitely long tape, that has been divided up into cells. Each cell can contain either a 1, a 0 or an empty space. Above one cell of the tape is a head, which can either move left or right, and can read the symbols written in the cells. The head is also capable of erasing symbols and writing new symbols into the cells.</p><p><img alt="Turing_machines_01.gif" src="/static/Turing_machines_01.gif" /></p><p>The direction that the head moves, which values it erases, and which values it writes in, are dependent on a set of instructions provided to the machine.</p><p>Different sets of instructions can be divided into <strong>states.</strong> States are like sub-routines and can themselves feature as part of instructions.</p><p>For example:</p><h3 id="state-2">State 2</h3><ul><li>If 0 then erase</li><li>Write 1 then move right</li><li>Go to state 5</li></ul><h3 id="state-5">State 5</h3><ul><li>If 1, then erase</li><li>Write 0 then move left</li><li>Go to state <em>n</em></li></ul><p>Alan Turing proved that <strong>any problem that is computable</strong> can be computed by a Turing Machine using this simple system.</p></div></article><nav class="ui attached segment deemphasized backlinksPane" id="neuron-backlinks-pane"><h3 class="ui header">Backlinks</h3><ul class="backlinks"><li><span class="zettel-link-container cf"><span class="zettel-link"><a href="Turing_completeness.html">Turing Completeness</a></span></span><ul class="context-list" style="zoom: 85%;"><li class="item"><div class="pandoc"><p>We know that a <span class="zettel-link-container cf"><span class="zettel-link" title="Zettel: Turing Machines"><a href="Turing_machines.html">Turing machine</a></span></span> is a theoretical construct of a computer that:</p></div></li></ul></li><li><span class="zettel-link-container cf"><span class="zettel-link"><a href="The_History_of_Computing_Swade.html">History of Computing (Swade, 2022 )</a></span></span><ul class="context-list" style="zoom: 85%;"><li class="item"><div class="pandoc"><p>Technical design provided by Alan <a href="z:tag/Turing" title="cf">z:tag/Turing</a> working at the Mathematics Division of the National Physical Laboratory. The product of Turing’s theoretical work in “On Computable Numbers” where he proposes the concept of a <span class="zettel-link-container cf"><span class="zettel-link" title="Zettel: Turing Machines"><a href="Turing_machines.html">Turing_machine</a></span></span> and based on his experience with early single-purpose computing devices at Bletchley.</p></div></li></ul></li></ul></nav><nav class="ui attached segment deemphasized bottomPane" id="neuron-tags-pane"><div><span class="ui basic label zettel-tag" title="Tag">Turing</span><span class="ui basic label zettel-tag" title="Tag">theory-of-computation</span></div></nav><nav class="ui bottom attached icon compact inverted menu blue" id="neuron-nav-bar"><!--replace-start-9--><!--replace-end-9--><a class="right item" href="impulse.html" title="Open Impulse"><i class="wave square icon"></i></a></nav></div></div><!--replace-end-6--><!--replace-end-3--><!--replace-end-2--><div class="ui center aligned container footer-version"><div class="ui tiny image"><a href="https://neuron.zettel.page"><img alt="logo" src="https://raw.githubusercontent.com/srid/neuron/master/assets/neuron.svg" title="Generated by Neuron 1.9.35.3" /></a></div></div></div></body></html> |