chapter 11 fluency with information technology 4 th edition by lawrence snyder (slides by deborah...
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![Page 1: Chapter 11 Fluency with Information Technology 4 th edition by Lawrence Snyder (slides by Deborah Woodall : woodall@mc.edu) 1](https://reader036.vdocuments.site/reader036/viewer/2022082710/56649e795503460f94b79ab6/html5/thumbnails/1.jpg)
Chapter 11
Fluency with Information Technology4th edition
by Lawrence Snyder(slides by Deborah Woodall : [email protected])
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Its about Bits…
1 High circuit Magnetized spot bump0 Low circuit Demagnetized spot land
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And Mostly Manipulating Bits…
• ASCII characters– Bit patterns assigned arbitrarily.– Bits are not manipulated.
• Numbers, colors, images, video– Bit patterns are not arbitrary.– Bits are manipulated with mathematics.
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Remember the Number Systems?
• Decimal number system– We know this!– base 10– 10 symbols 0 - 9– e.g. 1,375
The place values of 1, 3 7 5 are…
103 102 101 100
And it can be written in expanded form as
(1 * 103) + (3 * 102) + (7 * 101) + (5 * 100)
• Binary number system– Remember this?– base 2– 2 symbols 0 – 1– e.g. 1001Similarly the place values of 1001
are… 23 22 21 20
And it can be written in expanded form as
(1 * 23) + ( 0 * 22) + (0 * 21) + ( 1 * 20)
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Colors
• A color code is 3 bytes: RGB (byte 1 for Red, byte 2 for Green, byte 3 for Blue)
• 3 bytes = _________bits
• The lower the number in the byte, the lower the intensity of that color.
• The fact that a color is a group of bits means we can handle a color like a number – doing arithmetic to manipulate the color.
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Colors
• Black Red byte Green byte Blue byte
Binary: 0000 0000 0000 0000 0000 0000Hexadecimal: 00 00 00Decimal: 0 : 0 : 0
• WhiteBinary: 1111 1111 1111 1111 1111 1111Hexadecimal: FF FF FFDecimal: 255 : 255 : 255
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Colors
• RGB values where R = G = B are gray
• If we ADD the same value to each byte we get a lighter gray.
• If we SUBTRACT the same value from each byte we get a darker gray.
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Adding Binary Numbers
Addition Facts
0+0 0
0+1 1
1+0 1
1+1 10
11
+111
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Adding Binary Numbers
1 01 11 1 0 01 1 1+0 0 1 1 1 0 1 0 1 1 1 0 1 1 0 1
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Adding to Gray
Gray: 0011 1001 0010 1001 0010 1001 +0111 1010 +0111 1010 +0111 1010Lighter Gray: 1011 0011 1011 0011 1011 0011
Look at the Moon Photo discussion in the text.
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Overflow
• Overflow occurs when the computer does arithmetic and the answer will not fit where it needs to go.
• Software should handle overflow in a reasonable manner.
• Allowing sufficient bytes for the answer is a common way to handle it.
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File Compression
• To compress a file means to reduce the number of bits in the file, thereby making it take up less space.
• Mathematics is used to do file compression.
• This is especially important for files downloaded over the Web, or those stored in limited space like a CD or DVD or camera memory card.
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Sound
• Mathematics is used to compress, clean up and change sound.
• Sound is a continuous vibration causing a pressure wave.
• The input device samples the wave at regular intervals storing a long sequence of bytes in memory.
• Sampling Rate=the number of samples taken per second
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Sound
Sound In• The sound wave is detected
by a microphone.• The microphone converts
the sound wave into an equivalent electrical wave.
• The electrical wave goes into an analog-to-digital converter for sampling.
• The binary samples go into RAM.
Sound Out• The binary samples come
from RAM.• They go into a digital-to-
analog converter.• The DAC creates an
electrical wave using interpolation.
• The electrical wave goes to a speaker which vibrates creating the sound wave.
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Sound
MP3 (MPEG level 3) compression• One of the most popular compression
techniques for music• Removes sounds we cannot hear and noise• Resulting file is about 1/10 the size of the
original• A lossy compression technique
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Images
An image file is a long sequence of RGB pixel data.
Mathematics is used to manipulate and compress image files.
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Images
JPEG compression– One of the more common compression
techniques for images– Best for photos and complex graphics– The resulting file is about 1/20 the size of the
original file– Amount can be controlled– An overall lossy compression technique
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Run-Length Compression
Which representation takes up less space?r1g1b1 r2g2b2 r2g2b2 r2g2b2 r2g2b2 r2g2b2 r2g2b2 r2g2b2
r2g2b2 r2g2b2 r2g2b2 r2g2b2 r2g2b2 r2g2b2 r3g3b3
Or
r1g1b1 [13 * r2g2b2] r3g3b3
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Images
GIF compression• Another commonly used compression technique
for images
• A lossless compression technique
• Best for icons, cartoons, and simple graphics
• Strictly uses run-length encoding.
• PNG format may eventually replace GIF
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Video
MPEG ( MPEG-2, MPEG-4 ) compression• A commonly used compression technique for
video
• Records differences between frames
• A lossy compression technique
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