Bits are Not just for Numbers
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Computers store characters as bits or binary digits.
Characters from the English-language keyboard are
represented in ASCII as a series of 7-bits. This includes
letters, numbers and “special” characters.
Computers perform arithmetic in binary (base 2) rather
than decimal (base 10).
101
+10
----------111
Copyright © 2008 by Helene G. Kershner
1100 . 10
+ 10 . 10
--------------1111 . 10
Bits are Not just for Numbers
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The World of computers is filled with more than
characters and binary numbers.
What else is it filled with?
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Color
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Pictures
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Sound.
Copyright © 2008 by Helene G. Kershner
Bits are Not just for Numbers
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All computer data is represented using bits.
Bits can only have two states, on/off, 0/1, black/white,
color on/color off.
Everything is made up of bits, numbers, letters, symbols,
pictures, videos, sound, music ….
Copyright © 2008 by Helene G. Kershner
Bits are Not just for Numbers
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Screen images:
 Whether we display text or graphics on the screen,
all are created as a series of closely placed dots of
light.
 A pixel, is a dot of light on a computer screen.
Pixel is short for picture element.
 Resolution is a measure of pixel density on a
screen.
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The more pixels per square inch, the higher the resolution
of a screen image, and the clearer and crisper it appears.
A traditional monitor displays an image made up of 1024
columns and 786 rows of pixels. This is a pixel density or
1024 x 768 or 786,432 lighted dots.
Copyright © 2008 by Helene G. Kershner
Bits are Not just for Numbers
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Images:
 Black and white TV, and early computer monitors
used lighted pixels of a single color to produce
images.
 Early computer monitors were not necessarily black
and white.
Today the “world” is in color.
 Well sort of…..
Copyright © 2008 by Helene G. Kershner
Bits are Not just for Numbers -- Images
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When displaying graphics, picture and images, a
technique called gray-scaling is used. This is much
like a “black and white” photograph, where colors are
represented not as pure black and white but rather as
shades of gray.
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Grayscale images vary “from black at the weakest intensity to
white at the strongest, though in principle the samples could
be displayed as shades of any color” *
Grayscale is NOT black and white, which would be only those
colors.
* http://en.wikipedia.org/wiki/Grayscale
Copyright © 2008 by Helene G. Kershner
Bits are Not just for Numbers -- Images
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Color:
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Most color monitors use a red-green-blue (RGB) format.
When these three colors of light are mixed, white light is
produced.
A wide range of colors can be obtained by mixing these three
colors. *
* http://en.wikipedia.org/wiki/RGB_color_model
Copyright © 2008 by Helene G. Kershner
Bits are Not just for Numbers -- Images
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Color:
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Color requires independent, integrated hardware to light the differentcolored pixels in the desired combinations.
Keeping track of and controlling the more complex hardware, requires a
color graphics card manage to he pixels.
All of this management requires additional dedicated memory.
RGB
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The specific color that a pixel describes is some blend of three colors of
light (red – green – blue)
Up to three bytes (8-bits each) of data can be used to specifying a
pixel's color. 1
One byte for each major color component.
A true color or 24-bit color system uses all three bytes.
Many color monitors use only one byte (8-bits) for each pixel limiting the
monitor to only 256 (28) different colors. 2
1 A definition from Whatis.com
2. http://www.webopedia.com/TERM/P/pixel.html
Copyright © 2008 by Helene G. Kershner
Bits are Not just for Numbers -- Images
Copyright © 2008 by Helene G. Kershner
Bits are Not just for Numbers -- Images
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http://www.lovepixels.pwp.blueyonder.co.uk/
Copyright © 2008 by Helene G. Kershner
Bits are Not just for Numbers -- Images
grayscale
true color
http://en.wikipedia.org/wiki/Bits_per_pixel
Copyright © 2008 by Helene G. Kershner
Bits are Not just for Numbers -- Sound
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What is sound?
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Sound is a wave
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Sound waves move through the air
Sound waves move through other materials
Sound is vibration
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The sound of our voice is the vibration made by our vocal chords
A door moving back and forth
The wind
A musical instrument
 Vibrating wire
 Vibrating reed
 Vibrating lips
Copyright © 2008 by Helene G. Kershner
Bits are Not just for Numbers -- Sound
What is a sound wave? It’s a wave of sound. Music is just a
bunch of sound waves, arranged in a nice pattern.
www.globalsecurity.org/.../ship/acoustics.htm
Copyright © 2008 by Helene G. Kershner
http://library.thinkquest.org/06aug/02101/physics_soundwaves.htm
Bits are Not just for Numbers -- Sound
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Digital Sound
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If sound is a wave, then it is analog, it is something created in the
“real” rather than the virtual world of computers.
 Sound on a dial telephone was analog, and the sound wave actually
travelled over the wires
 Digital sound is an approximation of the sound wave using on/off
pulses (our bits again)
The wave is light gray.
The digital equivalent
is in red.
http://en.wikipedia.org/wiki/Digital_audio
Copyright © 2008 by Helene G. Kershner
Bits are Not just for Numbers -- Sound
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Digital sound is an approximation of the sound wave using on/off
pulses (our bits again)
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Each part of the sound wave is represented by a number of bits
The more the wave is broken up into pieces (sample), the more
accurate the sound.
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CDs use 16-bits/sample
DVD-Audio uses 24-bits/sample
http://en.wikipedia.org/wiki/Digital_audio
Copyright © 2008 by Helene G. Kershner