It is an interface between hardware and user and according to which different peripherals devices perform their function. It provides environment for program development and execution and performs device management, memory management, resource sharing.
Types of OS:-
- Batched os
- Distributed os
- Real time os
- Timesharing os
- Multi Programmed os
- Windows XP
- Windows 7
- Windows Vista
- Mac OS
OS will be mainly divided into two parts user + kernel
Kernel manages the communication between hardware and software components. Kernel is a part where all OS services are stored. A User is an human agent who uses the operating system. User is a part where all user related services are stored.
Types of kernel:-
- Monolithic kernel: In monolithic kernel, all OS services run along with the main kernel thread. This approach provides rich and powerful hardware access. The main disadvantage of this kernel is the dependencies between system components- a bug in a driver might crash the whole system. Examples of this kernel is UNIX.
- Micro kernel : A micro kernel designed for specific platform or device on only ever going to have what it needs to operate. The functionality of micro kernel OS contains a set of servers that communicate through a minimal kernel, leaving as little as possible in 'system space' and as much as possible in 'user space'. Micro kernel are easier to maintain than Monolithic kernel.
OS has many other features like scheduling, is done to load balance a system effectively or achieve a target quality of service and there is a scheduler which is concerned mainly with:latency ,response time,waiting time.
- Throughput -The total no.of processes that complete their execution per time unit.
- Response Time -Amount of time it takes from when a request was submitted until the first response is produced.
- Latency Time -Turn around time + response time
- Waiting Time -Time for which process remain in the ready queue.
OS Components:-
- Process Management
- File Management
- Main Memory Management
- I/O Management
