the user to interact with the hardware so that they can send commands (input) and receive results (output). It provides a consistent environment for other software to execute commands. OBJECTIVES OF OPERATING SYSTEM 1. Interface between the user and the hardware 2. Coordinate hardware components 3. Provide environment for software to function 4. Provide structure for data management 5. Monitor system health and functionality FUNCTIONS OF OPERATING SYSTEMS: Following are some of important functions of an operating System. 1. Memory Management 2. Processor Management 3. Device Management 4. File Management 5. Security 6. Control over system performance 7. Job accounting 8. Error detecting aids 9. Coordination between other software and users COMPUTER-SYSTEM ARCHITECTURE: A computer system can be organized in a number of different ways, which we can categorize roughly according to the number of general-purpose processors used 1. Single-Processor Systems 2. Multiprocessor Systems 3. Clustered Systems OPERATING SYSTEM STRUCTURE: The design of operating system architecture traditionally follows the separation of concerns principle. This principle suggests structuring the operating system into relatively independent parts that provide simple individual features, thus keeping the complexity of the design manageable. A. Simple Structure B. Layered Approach C. Micro-kernels D. Modules