what is an operating system?

Operating system is nothing but a program which is use to control the hardware or resources very efficiently.

BOOTING PROCEDURE:-
when a computer is rebooted or powered up it needs an initial program to run.this initial program is called bootstrap program.typically it is stored in ROM.it initialises the CPU registers,device controllers,memory contents etc.the bootstrap program must know how to load the operating system and to start executimg the program.modern operating systems are interrupt driven.if there are no processes to execute,no I/O devices to service,and no users to whom to respond to,the operating system will not do anything and will sit quietly waiting for any event to occur .events are always signaled by interrupt or trap.

BASIC WORKING:-
whenever any event or interrupt occurs the operating system will check for the resources requested by the process or event or interrupt.if the resources are there then the interrupt or event will be processed,otherwise the process will be kept on wait.lets take an example:-
suppose you try to print a document,the operating system will check for the recources,here the resources is printer and the printer pages. if the recourses are ready then the process will be done immediately otherwise the process will be kept on wait and also can be suspended after some time.