interruptservice

An interrupt service routine, often abbreviated as ISR, is a software routine that a computer system executes in response to an interrupt. An interrupt is a signal to the processor emitted by hardware or software indicating an event that needs immediate attention. When an interrupt occurs, the processor suspends its current execution and transfers control to the ISR. The ISR then performs the necessary actions to handle the interrupt, such as reading data from a device or updating system status. Once the ISR completes its task, the processor typically resumes the interrupted program from where it left off.

The primary purpose of an ISR is to provide a timely and efficient response to external events without requiring the processor to constantly poll devices for status changes. This polling method, known as busy-waiting, consumes significant processor time unnecessarily. Interrupts allow the processor to perform other tasks while waiting for an event to occur. Common sources of interrupts include keyboard presses, mouse movements, network packet arrivals, disk I/O completion, and timer expirations.

When an interrupt occurs, the hardware typically signals the processor through an interrupt request (IRQ) line. The processor then identifies the source of the interrupt and, based on a lookup table or a similar mechanism, jumps to the corresponding ISR. The ISR must be written to be very short and efficient, as it temporarily halts all other processor activity. After executing the ISR, the processor restores its previous state and resumes the interrupted task. The design and management of ISRs are crucial for the responsiveness and stability of modern operating systems and embedded systems.