User mode and Kernel Mode|Dual Mode of Execution
User mode and Kernel Mode|Dual Mode of Execution
System usually follow a dual mode of execution.User processes normally run in user mode and they are not given direct access to kernel space and hardware resources.For that process should switch to kernel mode of execution.Once in kernel mode,system has access to all devices ,kernel space and user space.For that user processes should request the kernel service with the help of system calls.And system calls are issued with software interrupts.So system calls,trap due to exceptions and hardware interrupts from devices are all handled in a same way.System switches from user mode to kernel mode and processor jumps to some handler routine kernel code corresponding to it.
see the complete series
Operating System-process synchronization at https://www.youtube.com
/watch?v=TLwuWlcnXjE&list=PLskQvPDUk0sJ6RRPdkgO2qziych6vQwZ1
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