Interrupt Service Routine (ISR)
An interrupt service routine (ISR) is a software routine that hardware invokes in response to an interrupt.
Interrupt Service Routines (ISRs) are fundamental components in the handling of interrupts in computer systems. When an interrupt occurs, the normal flow of program execution is temporarily halted and control is transferred to the corresponding ISR.
But how is the ISR implemented?
I can see how Polling is implemented.
See Interrupt Handling for the actual mechanism.