Task Switching
The IA32 processors provide automated mechanisms to handle the suspension of one task and the initiation of another. The OS creates a Task State Segment (TSS) for each task to be run. In a task's TSS, the OS programmer defines the following characteristics of the task:
The initial settings of the processor's registers.
The task's IO Permission Bit Map.
The task is launched by telling the processor the start address of its TSS. The processor then loads its register set from the TSS and begins execution of the program. When it's time to suspend a task and to start or resume another task, the processor first stores the current state of most of its registers in the TSS of the task being suspended. It then loads most of its registers ...
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