Informationsprocesser

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Informationsprocesser

• Kybernetik, informationsvidenskab og computerens
  fødsel

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Definitioner af kybernetik

• "the science of control and communication in the
  animal and the machine"- Norbert Wiener
• "Cybernetique the art of governing or the
  science of government" - A.M. Ampere
• "a branch of mathematics dealing with problems of
  control, recursiveness, and information" -
  Gregory Bateson
• "Cybernetics is the science of unseen processes
  which energize dynamic entities man-made,
  natural, and spiritual. In a narrower technical
  view, cybernetics are what makes systems
  function." - Charles A. Fink
• "Should one name one central concept, a first
  principle, of cybernetics, it would be
  circularity." - Heinz von Foerster

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Ross Ashby (1903-1972)

• Kybernetik ? Alle tænkelige maskiner
• Geometri ? Alle tænkelige objekter
• ? Biologi samme (organisations-)principper i alt
  liv
• Angår systemers opførsel og dynamik
• It does not ask what is this thing? but what
  does it do?
• ikke energi eller materialitet
• Cybernetics might...be defined as the study of
  systems that are open to energy but closed to
  information and control.

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Ross Ashby

• Feedback (dynamik)
• Homeostasis (ligevægt)
• State (tilstand)
• State-space (mulige tilstande)
• Trajectory (udvikling)

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The Watt Governor

• Pre-kybernetisk feedback regulator
• Dynamisk, ikke-computationel
• Termostat

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Informationsteori

• Claude Shannon (1917-2001) Ingeniør på Bell
  Labs Telefonkablers kapacitet
• Information Sum af sandsynligheden af signalets
  elementer (I - ? p(si)log(si))
• Information hviler på valg (forskel K, ikke et
  af de 28 andre bogstaver)
• Entropi Jo flere mulige mikro-tilstande, des
  mere information/entropi (mulige tal ?
  190/mulige partikelditributioner ? 190? C)

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Informationsteori

• The fundamental problem of communication is that
  of reproducing at one point either exactly or
  approximately a message selected at another
  point. Frequently the messages have meaning that
  is they refer to or are correlated according to
  some system with certain physical or conceptual
  entities. These semantic aspects of communication
  are irrelevant to the engineering problem. The
  significant aspect is that the actual message is
  one selected from a set of possible messages
• Shannon 1948

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Information

• Kvantitativt information angår ikke mening
• Information er kontekstuafhængig
• Information er ikke, hvad der bliver sagt, men
  hvad der kan siges

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Alan Turing (1912-1954)

• Engelsk logiker
• Bryder nazisternes kodesystem Enigma
• Står fader til datalogi (computation) og AI (og
  biologisk morfologi)

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Turing-maskine

• Imaginær maskine Software
• Hoved til aflæsning og indkodning (1)
• Strimmel med binære koder (2)
• Table of behaviours
• Tre parametre
• Tilstand (eks. 011)
• Kode på strimmel (eks. 0)
• Instruktion (eks. Hvis tilstand A, og kode 1 så
  skriv 0 og gå 3 felter til højre)

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2
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Den moderne computer

• 1941 Radiorør (? Bug)
• 1956 Transistorer
• 1958 Mikrochip
• 1970 Netværk
• 1971 Universel mikrochip
• 1979 Laptop
• 1981 PC
• 1984 Grafisk brugerflade (Macintosh)
• 1992 PDA
• 2002 ? Disappearing computers?