Tekno-logos 24/9-02 Informationsprocesser Kybernetik, informationsvidenskab og computerens fødsel

Tekno-logos 24/9-02 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

Tekno-logos 24/9-02 Ross Ashby ( ) 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”.

Tekno-logos 24/9-02 Ross Ashby Feedback (dynamik) Homeostasis (ligevægt) 1.State (tilstand) 2.State-space (mulige tilstande) 3.Trajectory (udvikling) 2 1 3

Tekno-logos 24/9-02 The Watt Governor Pre-kybernetisk feedback regulator Dynamisk, ikke- computationel ≈ Termostat

Tekno-logos 24/9-02 Informationsteori Claude Shannon ( ): 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)

Tekno-logos 24/9-02 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

Tekno-logos 24/9-02 Information Kvantitativt: information angår ikke mening Information er kontekstuafhængig Information er ikke, hvad der ‘bliver sagt’, men hvad der ‘kan siges’

Tekno-logos 24/9-02 Alan Turing ( ) Engelsk logiker Bryder nazisternes kodesystem Enigma Står fader til datalogi (computation) og AI (og biologisk morfologi)

Tekno-logos 24/9-02 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) 1 2

Tekno-logos 24/9-02 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?