An operation system is a set of programs which manages and controls the resources that are available in the computer. In other wards and operating system is and interface between the used and the computer.
Here the resources in the sense any device which is connected to the computer like keyboard, mouse, printer, scanner, webcam etc
If you want to work with computer we need any one of the operating system like DOS, windows95, 98,windows7 or windows 8 .Operating system is very essential to work with computer. Whenever we connect a device to the computer, first of all the operating system has to identify that particular device afterwards we have to install the device driver to work the device properly. Some operating systems supports multi users also.
To interact with the computer in dos we use commands and other operating systems it means all graphical operating systems we use mouse to work with the operating system.