Chapter_3(S) - Chapter3 DataRepresentation DataandComputers...

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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 discrete representation, 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 information by breaking it into pieces and representing those pieces separately. Why do we use binary? Modern computers are designed to use and manage binary values because the devices that store and manage the data are far less expensive and far more reliable if they only need to represent one of two possible values.
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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. 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.
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    8 Electronic Signals  (Cont’d) Periodically, a digital signal can be reclocked to regain its original shape. No such process is available for analog signals. An analog and a digital signal Degradation of analog and digital signals
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    9 Representing Text
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    10 Representing Text To represent a text document in digital form, we need to be able to represent every possible character that may appear. There is a finite number of characters to represent, so the general approach is to list them all and assign each a binary string. A character set is a list of characters and the codes used to represent each one. By agreeing to use a particular character set, computer manufacturers have made the processing of text data easier.
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    11 The ASCII Character Set ASCII stands for A merican S tandard C ode for I nformation I nterchange.
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