Operating System

What is an Operating System ?
The Operating System acts like an interface that cordinate the hardware and software. The computer interprets the instructions given by the user with the help of an operating system. Operating System acts as a central coordinator between hardware and Software. Hardware provides a user with basic physical resources to work upon. The application/utility software empowers the user to perform a variety of functions on the computer, such as solving problems, creating documents, playing games etc.

Features / Functions of an Operating System
The most popular operating systems, which are used nowadays, are, Windows 7, Windows 8, Windows 8.1, Windows 10, Mac OS X, and Linux. Most operating systems have certain features and functions in common. Some of the features are :

1. Processor Management
2. Memory Storage and Management
3. File Management
4. Device Management
5. Security and Protection
6. Enforcement of Priority System
7. Provision of User Interface
8. Job Control 

Types of Operating System
Operating System developed at a rapid pace to serve the needs of users. Following are the different types of operating system.

1. Single User Operating System
2. Multi- User Operating System
3. Multi- Processor Operating System
4. Multi- Tasking Operating System
5. Multi- Threading Operating System
6. Real Time Operating System (RTOS)
7. Distributed Operating System

1. Single User Operating System 
Single User Operating System was the inital version of the operating system that allowed only one user to work with the computer at a time. The most popular Single user Operating system were Microsoft DOS, Microsoft Windows 3.1, Microsofte Windows 95.

2. Multi- User Operating System
Multi - User Operating System allows more than one user to use the same computer at the same time or at different times. Some Operating Systems, which fall in this category are : Windows 2000, Windows NT, Windows XP, Windows Vista, Windows 7, Windows 8, Windows 8.1, Linux, Unix, Windows 2000 was the first version of Windows.

3. Multi- Processor Operating System
A multi- Processor system consistes of serveral processors, that share a coomon physical memory. In this system, all processors operate under the single operating system.
4. Multi- Tasking Operating System
An operating system, which is capable of doing multiple tasks or processes while using common processing resource, i.e., using onle one CPU is called a Multi- Tasking Operating system. Today, most operating systems fall under this category. Examples are Unix, Linux, Windows XP, Windows 7, Windows 8 , Windows 8.1, Windows 10 etc.

5. Multi- Threading Operating System
These Operating sytems allow different parts of a software program to run simultaneously. The feature of multi- threading can delay the execution respone of certain processes. The common examples of such operating systems are : Windows NT/2000, Windows XP, Windows 7, Windows 8, Windows 8.1, Unix, Linux etc.

6. Real Time Operating System (RTOS)
RTOS is designed to handle real life scenarios and problems. Such operating systems have the capability to prioritise the processes, minimise the execution time, and work independently with no interdependencies. 
Real time operating system is used when the time span required to react to an input is rigid and time bound. Even a microsecond of delay will cause the system to fail. Examples are : Air traffic control, Robots, Weapon systems and Industrial control systems.

There are two types of Real Time Operating Systems :
1. Hard Real - time system : These systems guarantee that critical tasks are completed in time.
2. Soft Real - time systems : These systems are less restrictive . Examples are : Undersea exploration, Plantary rovers and Virtual reality.

7. Distributed Operating System

Distributed operating system run on a set of computers that are located in different geographical areas, interconnected by a network. It controls these interconnected systems and makes them appear as a single computer.
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