When we turn on our computer installed operating system will start working. It ensures the co-ordination of other stored programs with system's hardware components.To enable operating system a Process is done which is called "Booting". It is performed by a software stored in our system BIOS(basic input-output system). BIOS does the following functions:
a)perform a Power-on self-test : this is done to make sure that other parts of computer are working properly or not.
b)It then checks if Rebooting is necessary or not,if not it does a Read/write test for RAM. While performing these operations you can see a black window showing some text.it is nothing but the information about CPU,memory and hard disks which given by BIOS software.After booting up, all control PC is given to Operating system.And now you are able to work on your personal computer.

the input/output proceser wil start the work....

@Rakesh,  Yes, thats why its posted over here. it will come under basic computer fundamentals.

hi,

When you turn on the power to a computer, the first program that runs is usually a set of instructions kept in the computer's read-only memory (ROM). This code examines the system hardware to make sure everything is functioning properly. This power-on self test (POST) checks the CPU, memory, and basic input-output systems (BIOS) for errors and stores the result in a special memory location. Once the POST has successfully completed, the software loaded in ROM (sometimes called the BIOS or firmware) will begin to activate the computer's disk drives.