1. Operating System

2. What is Operating System
An operating system (OS) is a collection of software that manages computer hardware resources and application programs and provides common services for computer programs. Eg: MS-Windows MS-DOS UNIX MAC-OS etc

3. Program Execution
Operating systems provides an environment where the user can conveniently run programs. Operating system takes care of the chores like memory allocation or multitasking or anything. Relieving the user from this burden.

4. I/O Operations
The operating systems hides the user the details of underlying hardware for the I/O.
All the user sees is that the I/O has been performed without concern by the user of the underlying details.

5. File System Manipulation
The reading and writing to/from a file involves the exchange of information to/from secondary storage devices.
The operating systems here makes it easier for user programs to accomplished their task that involves the services of secondary storage management.

6. Communications
Operating systems helps communication between processes , when they need to exchange information.
The processes may be on the same computer or on the different computers.

7. Error Detection
An error may cause a failure in the functioning of system.
Operating system constantly monitors the system for detecting the errors, their level and severity and takes appropriate actions according to the error.