How are interrupt handled by the operating system?

The fundamental interrupt mechanism works as follows:

The CPU hardware has wire called the interrupt-request line which the CPU senses after executing instruction. The device controller increases an interrupt by asserting a signal on the interrupt request line. Center proceeding unit detects that a controller has asserted a signal on the interrupt request line.

Interrupt driven input-output cycle

The CPU saves minute amount of state, as the current value of the instruction pointer i.e. return address, and jumps to the interrupt handler routine at fixed address in memory. The interrupt handler finds the cause of the interrupt performs the essential processing and executes a return from interrupt instruction, thereby clearing the interrupt. The CPU restarts to the execution state prior to the interrupt.