Operating Systems/Booting

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Overview[edit | edit source]

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After powering on, the first series of steps a computer goes through is known as booting. During the boot process, the system will load some form of startup instructions, then perform a series of common steps to prepare and load the operating system.

Common Steps[edit | edit source]

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While each computer system has a slightly different boot process, they all go through a set of common steps, outlined below.

1) The user, an internal timer, or some other event activates the power to the system.

2) The CPU performs a self test.

3) The system loads an initial set of instructions from a Read Only Memory (ROM). On the x86 IBM/PC compatible systems, this is the BIOS.

4) The startup instructions initialize the video card (if present) or other output device and performs a series of system self tests.

5) The startup instructions locate, load, and pass control to the boot loader.

6) The boot loader initializes the system to a known state.

7) The boot loader locates, loads, and passes control to the operating system kernel.