Presentation Layer

The sixth layer of the OSI Reference Model is the presentation layer. The presentation layer is responsible for defining how information is presented to the user in the interface that they are using. This layer defines how various forms of text graphics video or audio information are presented to the user. For example text is represented in two different forms: ASCI and EBCDIC. ASCII (the American Standard Code for on formation interchange used by most devices today) uses seven bits to represent characters. EBCDIC (Extended Binary- Coded Decimal Interchange Code developed by IBM) is still used in mainframe environments to represent characters. Text can also b shaped by different elements such as font underline italic and bold. There are different standards for representing graphical information BMP, GIF, JPEG, TIFF and others. This variety of standards is also true of audio (WAV and MIDI) and video (WMV, AVI, and MPEG). There are literally hundreds of standards for representing information that a user sees in their application. Probably one of the best examples of applications that have a very clear presentation function is a web browser since it has many special marking codes that define how data should be represented to the user. The presentation layer can also provide encryption to secure data from the application layer however this is not common with today methods of security since this type of encryption is performed in software and required a lot of CPU cycles to perform