Basic Concept OF Operating System

An operating system is a set of instructions stored on a storage device such as hard disk, Compact Dist  Read Only Memory (CD ROM) or floppy disk . When you switch on a computer , the power on routing activates and a set of a power -on routine activities is performed . These power -on routine
activities verify the devices attached to the CPU , such as keyboard, hard disk, floppy disk. CD ROM and printers for their proper functioning. The instructions for these power-on routine activities are stored in the
Read Only Memory is permanent in nature and stores the data even when the power is switched off.
However, ROM stores only few kilobytes of  instructions due to its finite size . AS a result , the power -on
routine activities are stored permanently in the hard disk as operating system, and are transformed from the hard disk into the Random Accese Memory (RAM) on booting the computer system