Q. Explain about Interrupt servicing routines?
First the situation is to be checked as to why the interrupt has happened. That includes not only device but also why the device has prompted the interrupt. Once the interrupt condition is recognized the necessary program known as ISRs (Interrupt servicing routines) should be executed such that CPU can resume further processing.
E.g. presume that interrupt happens because of an attempt by an executing program for execution of an illegitimate or privileged instruction then ISR for such interrupt can terminate execution of program which has caused this situation. So on event of an Interrupt related ISR is executed by CPU. ISRs are pre-defined programs written for particular interrupt conditions.