3. 4.3 Process Switching( 2/3) Mode switching User Mode->Kernel Mode 1. Interrupt Clock interrupt: process has executed for the maximum allowable time slice ·I/ O interrupt Memory fault: Referenced virtual address is not in main memory, so it must be brought in 2. Trap error or exception occurred, may cause process to be moved to exit state 3. Supervisor call (System Call such as file open3.4.3 Process Switching（2/3) • Mode Switching: User Mode -> Kernel Mode • 1. Interrupt • Clock interrupt: process has executed for the maximum allowable time slice • I/O interrupt • Memory fault: Referenced virtual address is not in main memory, so it must be brought in. 2. Trap • error or exception occurred, may cause process to be moved to Exit state 3. Supervisor call (System Call) • such as file open 11