Bits are Not just for Numbers
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Computers store characters as bits or binary digits.
Characters from the English-language keyboard can be
represented in ASCII as a series of 7-bits. This includes
letters, numbers and “special” characters.
Unicode the common coding system because it expands
the possible character set. All Internet operations use
Unicode.
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.
Copyright © 2008 by Helene G. Kershner
Bits are Not just for Numbers
 Resolution
is a measure of pixel density on a
screen.
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.
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Bits are Not just for Numbers
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Images:
 Black
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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
grayscale
true color
http://en.wikipedia.org/wiki/Bits_per_pixel
Copyright © 2008 by Helene G. Kershner
Bits are Not just for Numbers -- Images
Here the pixels are visible to the eye
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http://www.youtube.com/watch?v=m0S0qg4Zh7Y
Here the pixels are essentially invisible
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http://www.youtube.com/watch?v=avMW_hKtcDM
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