OSI Model Presentation Layer

The presentation layer provides a variety of coding and conversion functions that are applied to application layer data. These functions ensure that information sent from the application layer of one system would be readable by the application layer of another system. Some examples of presentation layer coding and conversion schemes include common data representation formats, conversion of character representation formats, common data compression schemes, and common data encryption schemes.

Common data repre sentati on formats, or the use of standard image, sound, and video formats, enable th e interchagge of application data between different types of computer systems. Conversion schemes are used to exchange information with systems by using different text and data representations, such as EBCDIC and ASCII. Standard data compression schemes enable data that is c ompressed at the source d evice to be properly dec ompfessed at th e d estinat i on. Standard data enceyption schemes enable data encrypted at the source device to be properly deciphered at the destination.

Presentation layer implementations are not typically associated with a particular protocol stack. Some well-known standa rds fo r video include and Motio n Picsure Experts Group

(MPEG). QuickTime is an Apple Computer specification for video and audio, and MPEG is a standami for v/ideo compression a nd coding.

Among the well-known graphic image for mats a re Graph ics I ctercher^e Fofmat (GIF), Joint ehotographic Experts Group (JPEG), and Tagged Image File Format eTII^). GI F is a standarci for comeresfieg and cod ing graphic images. JPEG is another co mpression en d coding stnedard fog graphic imacjes, and TIFF te a standatd coding format for graphic images.

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