Question

Q2. According to your textbook, “...modern operating systems are interrupt driven.”

2 (a) What is an interrupt?

(b) Name two sources or triggers of interrupts, and give one example of each.

(c) Briefly describe what happens when an interrupt occurs.

Answer 1

a) Interrupt: An interrupt is a special signal generated by hardware or software program to interrupt the current ongoing process and take into consideration the request done by other processes.

b) The two main sources of interrupt are
:=> External interrupts: It occurs due to external calls from I/O devices. eg- power failure

=> Software interrupts: It occurs when an illegal operation is performed such as division by zero, stack overflow.

c) The following steps take place when an interrupt occurs:

=> Currently executing program is closed and all the flag and register value are saved ina stack.

=> It fetches the address of the interrupt service routine from the interrupt vector table.

=> Then it executes the interrupt service subroutine.

=> After the execution of the interrupt service subroutine is completed it fetches the contents of the previously executing instruction from the stack.

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