Chap 14 Presentation Layer Andres, Wen-Yuan Liao Department of Computer Science and Engineering De...
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Chap 14 Presentation Layer Andres, Wen-Yuan Liao Department of Computer Science and Engineer ing De Lin Institute of Technology [email protected] http://www.cse.dlit.edu.tw/~andres
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Transcript of Chap 14 Presentation Layer Andres, Wen-Yuan Liao Department of Computer Science and Engineering De...
Chap 14 Presentation Layer
Andres, Wen-Yuan Liao
Department of Computer Science and Engineering
De Lin Institute of Technology
http://www.cse.dlit.edu.tw/~andres
Overview
The presentation layer is concerned with the format and representation of data
Code formatting and conversion
Data structures that are used by applications
The Presentation Layer
Presentation layer functions and standards
File formats
Data encryption and compression
Functions and standards
The presentation layer is responsible for presenting data in a form that the receiving device can understand
Functions
Data formatting (presentation)
Data encryption
Data compression
Data Format
EBCDIC
ASCII
Layer 6 provides the translation between these two different types of codes
Graphic images
PICT MAC operating system
TIFFHigh-resolution, bit-mapped images
JPEG Compress still images of complex
pictures and photographs
GIF
Sound and movies
MIDI Digitized music
MPEG Standard for the compression and coding
of motion video for CDs and digital storage
QuickTime Handles audio and video for programs on
both MAC and PC operating system
File Formats
Text format: ASCII and EBCDIC
Binary files Display images - Graphic
Interchange Format (GIF), and Joint Photographic Experts Group (JPEG)
File FormatsMultimedia file formatDownloaded, first, and then playedStreaming audio
They may download while they are playing
WAV: sound
AVI: animation files
Video formats: MPEG, MPEG2, and Macintosh QuickTime
File Format - Markup language
Acts as a set of directions that tell a Web browser how to display and manage documents
HTML directions tell a browser whether to display text, or to hyperlink to another URL
Data encryption and compression
Data encryption protects information during its transmission
Compression works by using algorithms to shrink the size of the files
Summary
Determines how graphic images, sound and movies are presented
Provides encryption of data
Compresses text and converts graphic images into bit streams
