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02-TheEssentialQuestion-WhatAreWeComputing.md

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THE ESSENTIAL QUESTION IN COMPUTING - What Are We Representing with Digital Information?

  • Everything in computing is REPRESENTING digital information "as" something else.

  • Kinds of representations through history:

    DIGITAL COMPUTER TECHNIQUES & PRINCIPLES 1962 U.S. NAVY FILM UNIVAC IBM ELECTRODATA

    • Knots & Beads on a string - prehistoric, 6000 BC to 1500 AD

    • Physical indentations in clay — 8000 BC to 100 AD

    • Beads on an abacus - 3000 BC to present

    • Ink Marks on paper - 3000 BC to present

    • Positions of sticks seen at a distance (Semaphores) - 1790s to 1850s

    • Punched Holes in a paper card - 1800s to 1970s

      • Vast improvement over the paper ledger

      • Collection of data was standardized, fast and could be read by a machine

      • Data collected from the 1890 US Census was the first large scale use of punched cards

      • Allowed for the first "programmable" machines that could be used to perform relatively complex tasks like sorting and counting of specific data

    • Remnants of photons hitting a piece of glass coated with a thin layer of phosphor - 1940s to 1980s

    • Magnetic Phenomenon - 1950s to present

      • Electronically detectable areas on magnetizable material, or the presence of a magnetic field in a specific area

        Magnetic Fields "Bending" Light Paths

      • Core Memory - 1955 to 1975

      • Magnetic Tape - 1928 to present

        • "Sequential" access to data, like a cassette tape or a VHS tape.

        The Magnetic Tape Viewer - see the sound on a tape

      • Magnetic Disk - 1956 to present

        • "Random" access to data, like a record player or a CD player, and uses mechanical means to access the data

    • Tiny electrical charge of a capacitor (a simple gap between metal plates) in a tiny area of space - 1960s to present

      • DRAM (Dynamic Random Access Memory) Chip (10x magnification), not mechanical at all, just electrical.

  • Creating ANY machine capable of using "Boolean Logic" enables humans to create complex, custom general solutions to certain kinds of problems.

    • The problems must be able to be represented with binary information and the solution must be able to be represented with a series of logical operations.

    • By building up from the simple logic of AND, OR, and NOT operations, humans can create an arbitrarily complex sequence of logical operations.

    • These logical operations are sequenced in time to create "State Machines" that can perform complex tasks and solve complex problems. A state machine is simply a way of representing the problem that changes over time controlled by a series of logical operations & conditions that lead to certain states and available actions.

    • These logical operations are built up using patterns called "algorithms" grouped together in "programs" that can be executed by any digital computer, no matter what the underlying hardware is.

      All of this "technology" is based on human ingenuity and cleverness to exploit certain properties of naturally occurring phenomenon in a way to create some "useful human work".

      The machines cannot possibly "know" anything about the problem or solution, and NEVER WILL.

      It's just following the logical operations that humans have carefully designed to represent the problem and represent a solution.

  • Spiral Model of Development of Techniques in Computing

    • As knowledge and techniques in computing have developed, they have built upon each other in a spiral pattern.

    • Ideas and techniques from the past are often re-discovered and re-used in new ways.

  • Continue Reading - Hardware

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