1. Computer-System Operation - Each device controller in charge a specific device. - Interrupt indicates the occurrence from either the hardware or software.
2. Interrupt Handling - Fixed location contains starting address of the interrupt service routine. - Interrupt vector provide address of interrupt service routine.
3. Synchronous I/O Structure - Control returns to user program after I/O start and complete. - No simultaneous I/O process at a time , at most one I/O outstanding.
4. Modes of Operation 1. User Mode - User program executes in user mode. - Certain instruction may not be executed.
4.1. 2. Kernel Mode - Monitor executes in kernel mode. - Protected areas of memory may be accessed.
5. Memory Protection - Two register used o determine the range of legal address. -->Base register – holds the smallest legal physical memory address. --> Limit Register – contains the size of range. - Memory outside the defined range is protected
6. Asynchronous I/O Structure - Control returns to user program without I/O complete when I/O started. - Each entry of I/O device indicate its type , address, and state.
7. Dual-Mode Operation - Privileged instruction can be issued only in monitor mode.
