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Operating Systems Concepts - Engineering

Q1:

The CPU, after receiving an interrupt from an I/O device

A halts for a predetermined time

B hands over control of address bus and data bus to the interrupting device

C branches off to the interrupt service routine immediately

D branches off to the interrupt service routine after completion of the current instruction

E None of the above

ANS:D - branches off to the interrupt service routine after completion of the current instruction

When a device raises an interrupt at lets say process i, the processor first completes the execution of instruction I. Then it loads the Program Counter (PC) with the address of the first instruction of the ISR. Before loading the Program Counter with the address, the address of the interrupted instruction is moved to a temporary location. Therefore, after handling the interrupt the processor can continue with process i+1.