Application Layer

The application layer is the user's view of a computer.

We can view a program such as a word processor or spread sheet as a very specialized computer.

For example, here the GUI for the MS Excel spreadsheet:

We can think of a spreadsheet's main memory as a two-dimensional array of cells. The secondary memory are .xls files.

The data types include strings and numbers.

The instruction set consists of the commands on the menu.

The processor is the GUI's user input event loop.