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How Computers Work Part 1 6 February 2008 What does a Computer Do Well? Intelligence amplifier Does repetitive tasks quickly and correctly amplifies our ability to perform mental activities “power tools” for the mind Can process much more information Check things more quickly Removes people from boring tasks Manipulates forms and data What Wasn’t Possible Before? We can do things in virtual environments Chemists can see things at microscopic levels Micron: millionth of a meter Model weather Hurricane predictions Model historic events Marvelous Manipulator Manipulates form, not content When it appears to understand or apply judgment… Everything is a symbol Computers do not understand meaning Reflecting human knowledge that is encapsulated Programming: capturing our knowledge “expert systems” Examples from movies or books? What a Computer Does: Transforms IN Different reports from the same data Multiple inputs, one output Displaying a movie One input, multiple outputs OUT One input, one output PROCESS Computing a statistic Other examples? Thinking about Tools Write down a favorite tool or device Write down what it is intended to do Write down an alternative use Switch with a neighbor Write down another alternative Switch back Computers: The Most Adaptable of Tools Why? We can PROGRAM the computer Embedded computers Instructions are called software Programmed by the manufacturer General purpose computers Programmed by the consumer How Does a Computer Work? It is actually a very simple machine It executes exactly what it is told to do Forrest Gump “Run, Forrest, run” Forrest Computers execute algorithms What is an algorithm? A detailed sequence of actions to perform to accomplish some task Named after an Iranian mathematician, AlKhawarizmi 813 – 833 C.E. Mathematician: algebra, trigonometry, geometry Astronomy and geography as well Examples of Algorithms Mapquest directions Assembly instructions User’s manual Software program Other examples? A simple algorithm Using a calculator, how do you find the average of three numbers? Assume no average function Assume that the calculator is already on Solution Enter the first number; enter + Enter the second number; enter + Enter the third number; enter / 3 = A bigger example Using a calculator, how do you find the average of 100 numbers? No longer want to list one by one Introduces loops Solution For each number, Enter the number; enter + Enter / 100 = A more complex algorithm Take the absolute value of a number Introduces decision making Solution If the number is less than 0 The answer is –number Else The answer is number Simplified Model of a Computer retrieves the instruction directs data movement defines an algorithm Performs the operations processor Control Unit Arithmetic Logic Unit instructions data MEMORY the information that it works on and produces