Once all the required devices are properly connected to the main computer unit, you can switch o the system. Start the computer by first switching on the AC mains switch, power conditioning device (UPS, stabilizer etc.) switch and power on switch provided on the front panel or the back of the main system unit.
Turn on the monitor, turn on the Printer, the external modem, and the speaker if you require their service.
When the main unit is turned on you will hear the main unit power supply fan’s rotation sound. After some time the computer will produce a single beep sound to indicate that all its parts are working properly.
Before producing this beep sound, computer does a POST (Power On Self Test) operation. During POST, computer checks most of its parts to make sure that they are working normally.
During the POST, If the computer finds that a part is not working as expected, then it will display some error message or produces some combination of beep sounds to inform that something is wrong with the computer.
These beep sound combinations is called Error-Beep Codes.
If everything is all right with the computer then, after POST, the computer will produce a single beep sound.
After this beep, the computer needs a software called Operating System (OS). This Operating System or OS or DOS (Disk Operating System) is stored on some storage device such as a floppy disk, hard disk drive or CD-ROM is provided to the computer during the power on process.
Computer reads the Operating System (OS) from the storage device into its memory i.e. the RAM. This process of loading the OS from storage device into the computer memory is called “Booting of the Computer”.
This booting process is repeated whenever the computer is switched on, because every time power supply to the computer is switched of, the information stored in the computer’s memory (RAM) is lost.
Some of the OS available in the market are, MS-DOS, Linux, Unix, MS-Window, OS/2, DR DOS etc. Out of this operating systems the Windows developed by Microsoft Corporation is most common Operating System in the PC environment.
