What are the important main functions of an operating system?

The purpose of an operating system is to provide a platform on which a user can execute programs in a convenient and efficient manner.
An operating system has three main functions:
Operating system manage the computer’s resources, such as the central processing unit, memory, disk drives, and printers.
Operating system establish a user interface
Operating system execute and provide services for applications software.
The operating system uses password protection to protect user data and similar other techniques. it also prevents unauthorized access to programs and user data.
Operating system constantly monitors the system to detect errors and avoid the malfunctioning of computer system.
Operating systems also coordinate and assign interpreters, compilers, assemblers and other software to the various users of the computer systems.
An Operating System carries out the following file management activities. It keeps track of where information is stored, user access settings and status of every file.
The Operating System ensures the proper use of all the resources available by deciding which resource to be used by whom for how much time. All the decisions are taken by the Operating System.
An Operating System performs the following activities for processor management. It keeps tracks of the status of processes. The program which perform this task is known as traffic controller. Allocates the CPU that is processor to a process. De-allocates processor when a process is no more required.
The Operating System tracks an account of all the functionalities taking place in the computer system at a time. All the details such as the types of errors occurred are recorded by the Operating System.
All these services are ensured by the Operating System for the convenience of the users to make the programming task easier.