UNIVERSAL TURING MACHINE

UNIVERSAL TURING MACHINE

ANNOTATION |...| John Johnston, The Allure of Machinic Life: Cybernetics, Artificial Life, and the New AI, MIT, 2008 pp.70-73 Turing's 1936 paper on the Universal Machine was instrumental in arriving at a new understanding of a real-abstract machine. The Turing Machine: comprises three parts 1) a reading/writing "head" 2) an infinitely long "tape" divided into squares which pass along the head

3) a table of instructions (state transition table) which would tell the head what to do in relation to the machine's state. It would ask: is the mark absent or present on the tape? Depending on the outcome the machine encounters, it would

a) enter a mark

b) erase a mark

c) leave the square blank

The Turing Machine is the first example of a finite state machine. Data entering as a string of symbols (1 or 0) are encoded as absent or present. Instructions: If no mark = (state 1) enter mark, move to square on left = (state 2); if there is a mark move to square on the right and remain in state 2. The tape serves as a memory. Turing's thesis was that “every computation expressible as an algorithm, or every determinate procedure in a formal system, has its equivalent in a universal computing machine (aka Universal Turing Machine)” To return directly to Lacan and Seminar II, this universality makes it a new kind of machine which is defined by a logic or function rather than a material structure.

This, Lacan suggests, is a characteristic which such machines and humans share. But humans also have access to the imaginary-symbolic] a logical form which is given equivalence in a set of algorithms. < > Such machines can be made of many things. Johnston: "This behaviour is used to physically instantiate a symbol system with its own independent rules or syntax." A number of machines, from ENIAC (1946) to UNIVAC (1946) were automated, self-regulating arbitrary symbols combine to rules of composition – syntax, to produce more complex operations. In this way thinking machines automating the “laws of thought” unlike any previous machine.