How a computer starts: Behind the scenes

We all use computers pretty much everyday, but have you ever wondered what happens when you switch on a computer. Let us go behind the scenes and find out what happens inside the computer.

The BIOS chip
First of all the CPU performs a procedure called "booting" when the PC is turned on. The instructions for this come from BIOS(basic input/output system), a program stored on a flash memory chip (BIOS chip). Under booting the PC first performs POST (Power-on self-test). POST is a small program contained in the BIOS that checks for hardware failures. When the test is successful, the BIOS then locates the bootable drive to load the boot sector. The execution is then transferred to boot-loader (a computer program that loads an operating system) located in the boot sector. 

Booting is of 2 types: Warm and cold.

Warm booting: This booting takes place when a PC restarts. In this case the system does not start from the initial state, hence the diagnostic tests need not be carried out. This type of booting is often carried out when a program crashes.

Cold booting: This type of booting takes place when the system starts from the initial state, that is when it is switched on. Here the diagnostic tests are carried out. 

This post was designed to give an introductory info on PC booting. For more information check this out.

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