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Physical Transfer of Data on a Computer Bus

  1. Mar 1, 2010 #1
    My understanding of a modern computer is as follows; 'information' is sent from a keyboard as current (I), this signal is sent to the CPU via the appropriate buses (in this instance, USB -> North Bridge -> main bus/cpu bus -> CPU), which is then recognized by a CPU via integrated circuit, and each transistor recognizes this current as "on or "off" (0 or 1).

    My question:
    ...what is the current I that the computer sends? Is it classified as data, is it 01000010, or is it just a specific voltage? It seems to me that it would be charged electrons, not "data"

    Data only exists after the CPU deciphers the minute voltage differences that the keyboard sends to it, correct..? = x

    Then, assuming this is all right, what happens to the binary information from here? CPU firmware takes over and does what it does?

    This is for an independent research term paper (due next month), but i want an idea as to how my research is going so far.

    Thank you for reading

    edit: basic conceptual question; does data exist only in a CPU or hard drive? "Data" is only electricity unless otherwise decoded?
    Last edited: Mar 1, 2010
  2. jcsd
  3. Mar 1, 2010 #2


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    That's somewhat of a philosophical question. It's like asking "does a book contain a story if nobody is reading it?"
  4. Mar 1, 2010 #3


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    It's better to think in terms of voltages, rather than currents. Both are present, but information for the most part is represented by voltages inside the computer. The basic element is a "flip-flop" (FF), which is basically a 1-bit memory storage cell. In one form of logic, when the output of the FF is at 0 Volts, it is considered a logical "0". When the FF is in its other state, a logical "1", then its output voltage would be at 3.3 Volts (or whatever voltage the logic is running off of).

    In case you haven't done much reading yet, check out the pages at HowStuffWorks.com about computers and related things:


    If you have specific questions about your reading there or elsewhere, feel free to post your specific questions (and pointers to the reading) here.
  5. Mar 2, 2010 #4


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    Last edited by a moderator: May 4, 2017
  6. Mar 2, 2010 #5


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    For your specific example of a PC keyboard, there's a small cpu in the keyboard itself. It's constantly scanning the keys which are switches that are "closed" when keys are pressed. It then compares the results of each scan to a previous scan, noting any changes, such as a key pressed or released, then sends an encoded value for that event as a "scancode".

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