Chap 14 Presentation Layer Andres, Wen-Yuan Liao Department of Computer Science and Engineering De Lin Institute of Technology

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 TIFF High-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 Formats Multimedia file format Downloaded, first, and then played Streaming 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