Application Layer

This is the top layer of the OSI model. The application layer is only concerned with presenting information in human-friendly way. A more technical term is the ‘human-machine interface’ a rather grand way of saying the same thing.

Examples of the ‘Application Layer’. Don't forget, the OSI model is relevant to all kinds of devices, not just computers. The pictures below show that the Application Layer is relevant in mobile phones, iPods, computers, scientific instruments even audio players and so on. Can you think of some others?


A scientific interface	The Mac Dashboard	Windows XP

The iPod visual interface	An Audio Player interface	Mobile Phone interface

These are examples of a ‘Visual’ interface’.

Of course most people consider how something looks when they want to interact with it, but equally valid is an ‘Audio’ interface’.

For example listening to an internet radio show through headphones or speakers is another example of the application layer in action. Popular audio applications include ‘Windows Media Player’ and ‘WinAmp’.

The Application Layer receives its information from the ‘Presentation’ layer just below it.

When a person clicks \ selects a graphic button or icon on their screen, the application layer sends that information\event to the presentation layer beneath it. Its job is done - you have clicked \ selected something and now it is informing the Presentation layer of that fact.