Supervisor and User Mode

The process is executed in the modes supervisor and user mode. In supervisor mode control programs are executed. Actually in this mode the resource is given to user mode or used in a program. Command interpreter (shell), compiler, editor and similar application independent programs. These programs are not part of operating system but controlled by operating systems.

The operating system is that portion of software that runs in kernel mode or supervisor mode. The process or program is kernel mode is mode secure. In kernel mode, interrupt handling operation is performed. The interrupt handler is part of operating system.

To complete the task, the control switches from one mode to another for example in monolithic architecture of Os to complete a task two programs are divided into different events. In event 1, the control switches from user mode to kernel mode. After completing task by kernel than kernel gives o/p or control switches from kernel mode to user mode.

In kernel mode, all the instruction are allowed but in user mode only limited instruction are allowed I/O and contain other instruction may not be allowed. In case of monolithic architecture, I/O instructions are not allowed in kernel mode or supervisor mode.