Chapter03 - Chapter 3 Data Representation Data and...

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Chapter 3 Data Representation
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2 Data and Computers Computers are multimedia devices, dealing with many categories of information. Computers store, present, and help modify: Numbers Text Audio Images and graphics Video
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3 Analog and Digital Information Computers are finite. Computer memory and other hardware devices have only so much room to store and manipulate a certain amount of data. The goal of data representation is to represent enough of the world to satisfy our computational needs and our senses of sight and sound.
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4 Analog and Digital Information Information can be represented in one of two ways: analog or digital . Analog data: A continuous representation, analogous to the actual information it represents. Digital data: A series of discrete representations, breaking the information up into separate elements.
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5 Analog and Digital Information A mercury thermometer exemplifies analog data as it continually rises and falls in direct proportion to the temperature. Digital displays only show discrete information.
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6 Analog and Digital Information Computers cannot work well with analog information, so we digitize it by sampling it at discrete intervals and representing each interval by a numeric value.
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7 Electronic Signals An analog signal continually fluctuates up and down in voltage. But a digital signal has only a high or low state, corresponding to the two binary digits. An analog and a digital signal
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8 Electronic Signals All electronic signals (both analog and digital) degrade as they move down a line. That is, the voltage of the signal fluctuates due to environmental effects. Degradation of analog and digital signals
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9 Electronic Signals  (Cont’d) Even when it has deteriorated, it is possible to distinguish the 2 states of a digital signal by comparison to the threshold. Periodically, a digital signal can be reclocked to regain its original shape. No such process is available for analog signals.
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10 Representing Audio Data
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Representing Audio Information We perceive sound when a series of air compressions vibrate a membrane in our ear, which sends signals to our brain. A stereo sends an electrical signal to a speaker to produce sound. This signal is an analog representation of the sound wave. The voltage in the signal varies in direct
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This note was uploaded on 02/10/2012 for the course CSE CSE 1520 taught by Professor Paul during the Fall '09 term at York University.

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Chapter03 - Chapter 3 Data Representation Data and...

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