session 05 data representation - wordpress.com · 10/4/2015 · data representation • methods...
TRANSCRIPT
Session 05
Data Representation
Data Representation
• Methods used internally to represent information stored in a computer
• Different types of information
– Numbers
– Text
– Graphics (Picture, video, animation)
– Sound
– Data
• All types of information are stored in a computer through a sequence of 0's and 1's.
• Such value is called a binary digit or bit
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Data (0 and 1)
• Logically 0, 1
• Physically 0v , 5v
• Bit
– A bit is the smallest data on a machine 0 or 1
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Storage
8 Bits = 1 Byte
1024 Bytes = 1 Kilobyte (KB)
1024 KB = 1 Megabyte (MB)
1024 MB = 1 Gigabyte (GB)
1024 GB = 1 Terabyte (TB)
Example:
How many bits available for the 1.45 MB data file
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Number Systems
• Binary System { 0,1 }
• Octal System { 0,1,2,3,4,5,6,7 }
• Decimal System { 0,1,2,3,4,5,6,7,8,9 }
• Hexadecimal System
{ 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F }
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Number conversion
• Decimal to binary
• Decimal to Octal
• Decimal to Hexadecimal
• Example
13410 → 100001102, 2068, 8616
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Binary
OctalDecima
l
Hex decimal
Decimal /Octal/
Hexadecimal
• Binary to Octal
10 101 010 111
• Binary to Hexadecimal
101 0101 0111
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Data Representation
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Keyword Description Size/Format
byte Byte-length integer 8-bit two's complement
short Short integer 16-bit two's complement
int Integer 32-bit two's complement
long Long integer 64-bit two's complement
float Single-precision floating point 32-bit IEEE
double Double-precision floating point 64-bit IEEE
char A single character 16-bit Unicode character
boolean A boolean value (true or false) true or false
Integer numbers
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type Size Range
name bytes bits minimum maximum
byte 1 8 -128 +127
short 2 16 -32,768 +32,767
int 4 32 -2,147,483,648 +2,147,483,647
long 8 64 -9,223,372,036,854,775,808 +9,223,372,036,854,775,807
Character Representation
• ASCII
– American Standard Code for Information
Interchange (ASCII)
– 27 = 128 characters can be represented by ASCII
• Unicode
– Unicode: 16-bit system that can encode the
characters of most languages
– 16 bits = 216 = 65,636 characters
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ASCII
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Sinhala Unicode
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Example
• What are the ASCII Value for the following Name
– Budditha
• What are the ASCII Values for the following Keys
– Enter
– Scape
– Space
• What are the ASCII Value for the following Name
– සමරපාල
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Computer Images
Computational Model of Grammar for English to
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What is Computer image?
• visual representation of an object or scene or person
or abstraction produced on a surface
• Types
– Vector image
– Raster image
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Raster Images
• Raster image is used raster graphics to display
images
• data structure representing a generally rectangular
grid of pixels
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Vector Image
• vector graphics to display images
• geometrical primitives such as points, lines, curves,
and polygons, which are all based upon
mathematical equations to represent images in
computer graphics
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Colour representation
• RGB
• CMYK
• Lab
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RGB colour mode
• Red, Green, and Blue light are added together in
various ways
• three additive primary colors, red, green, and blue
• the RGB color model is the display of colors on a
cathode ray tube (CRT), liquid crystal display(LCD)
or plasma display
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CMYK Mode
• Cyan, magenta, yellow, and key (black)
• CMYK model works by partially or entirely masking
certain colors on the typically white background
• save money on ink, and to produce deeper black
tones
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Lab color
• individual channels: "L" indicates the luminance, "a"
the green-red chrominance and "b" the blue-yellow
chrominance
• well suited for modifying the brightness of an image
without changing the colours and saturation values
• Lab color is designed to approximate human vision
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Computer Images/ Graphics
• A computer screen consist of pixels
• Pixel has two properties: its location on the screen
and its color
• graphic image can be represented by a list of pixels
– A 16 color image requires 4 bits per pixel
– 24 bits per pixel, which provides an astounding
array of 16.7 million possible colors for each pixel
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Raster formats
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• Raster graphics image is a dot matrix data structure
representing a generally rectangular grid of pixels, or points of
color, viewable via a monitor, paper, or other display medium
• File Format
– JPEG (Joint Photographic Experts Group)
– TIFF (Tagged Image File Format)
– GIF (Graphics Interchange Format)
– BMP
– PNG (Portable Network Graphics)
Vector formats
• vector image formats contain a geometric
description which can be rendered smoothly at any
desired display size.
– SVG (Scalable Vector Graphics)
– PPT
– VML
– AI (Adobe Illustrator Artwork)
– CDR (CorelDRAW)
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Compound formats
• These are formats containing both pixel and vector data, possible other data, e.g. the interactive features of PDF.
– EPS (Encapsulated PostScript)
– PDF (Portable Document Format)
– PostScript, a page description language with strong graphics capabilities
– PICT (Classic Macintosh QuickDraw file)
– SWF (Shockwave Flash)
– XAML User interface language using vector graphics for images.
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Image Formats
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Audio Data
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Sound
• Analog signals are converted to digital signals at
a given sampling rate and bit resolution
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4 Bit
Sound file format
• File format for storing digital audio data on a
computer system.
• The bit layout of the audio data (excluding
metadata) is called the audio coding format and can
be compressed or uncompressed
• Format types
– Uncompressed audio format
– Lossless compressed audio format
– Lossy compressed audio format
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Audio file formats
• Uncompressed audio formats
– WAV, AIFF, AU or raw header-less PCM;
• Formats with lossless compression
– FLAC, WavPack, TTA, ATRAC, MPEG-4 SLS,
• Formats with lossy compression,
– Opus, MP3, Vorbis, Musepack, AAC, ATRAC and
Windows Media Audio Lossy (WMA)
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Video Files
• file format for storing digital video data on a
computer system.
• Video is almost always stored in compressed form to
reduce the file size.
• File format
– AVI
– MP4
– WMV
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Data file format
• Executable and link files
– EXE
– DLL
– COM
• Document files
– DOC
– DOTX
– PPT
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