Sunday, August 1, 2010

A Description of the Boot Process

The Boot process is the process which starts up the computer system, starting the computer's operating system and identifying its hardware and software components that all work together.


In order for a computer to successfully boot, its BIOS(Basic Input Output Operating System), operating system and hardware components must all be working properly; failure of any of these elements will result in a failed boot sequence.
When computer's power is turned on, the CPU initializes itself, which is triggered by a series of clock ticks generated by the system clock. Then the initialization looks inot the system's ROM BIOS for its first instruction in the startup program. The ROM BIOS stores the first instruction which then in turn runs pwer-on self test(POST), in a predetermined memory address.

POST checks BIOS chip and then tests CMOS RAM. If there is no battery failure detected during POST, then CPU is initialized followed by checking hardware devices, secondary storage devices such as hard drives, floppy drives, ports, keyboard and mouse to ensure they are functioning properly. Once the POST has determined that all components are functioning properly and the CPU has successfully initialized, the BIOS looks for an operating system to load

The order of drives that the CMOS looks in order to locate OS is called Boot Sequence.

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