Word-Processor Operation
In order to understand the operation of the PC microprocessor system, we will look at how the word-processor application uses the hardware and software resources. This will help us to understand the same basic processes that occur in microcontrollers.
Starting the Computer
When the PC is switched on, the RAM is empty. The operating system, application software and user files are all stored on the hard disk, so the elements needed to run the word processor must be transferred to RAM for quick access when using the application. The BIOS gets the system started. It checks that the hardware is working properly, loads (copies) the main operating system software (e.g. Windows) from hard disk into RAM, which then takes over. As you will probably have noticed, this all takes some time; this is because of the amount of data transfer required and the relatively slow access to the hard drive.