What are the three most important jobs of an operating system?

The operating system or OS is a software application that forms a layer between the hardware resources and the end user or the applications. OS is designed to perform three major functionalities which are described below.

1.Provides an interface for the end user

The operating system hides the complexities of the hardware resources of the computer. It acts as an interface through which the end user interacts with the hardware since it is not possible for the end users to directly interact and use the hardware resources of the computer.

It can be said that the operating system can lie at the top of the hardware resources. Also, the applications lie on top of the operating system. In addition to the user, OS acts as an interface for the software applications also.

2.Manages the hardware resources namely CPU, disk, memory and others

The operating system has the features to manage and maintain the resources of the computer including CPU, disk, memory, etc. The utility programs or the system software are applications which are developed to manage and maintain these resources.

Examples include disk fragmenter which takes care of the disks.

3.Execution of other applications

When an end user develops an application or operates tools like video camera, the user assumes that the application is being executed by the user. In reality, the operating system is responsible for proper functioning of the applications that run on top of the operating system.

It is the responsibility of the operating system to use the hardware resources and synchronize them so that the video camera can function as per the user requirements.  

Another aspect is multi-tasking. This refers to the ability of the operating system to execute more than one application at the same time. The applications need not think about the allocation and proper utilization of the resources. This is taken care by the OS.