Interrupt Requests

An interrupt operating system is a type of operating system that uses interrupt requests from hardware or software to manage resources, prioritize tasks and control input and output. Under an interrupt operating system, interrupts are received when an instruction needs to be executed, a device is requesting service or an error has occurred. The operating system pauses the current task and serves the request of the interrupt. Most modern operating systems are interrupt based.

Interrupt Request (IRQ) is a hardware line over which a computer's central processing unit (CPU) can send and receive signals to and from hardware devices. These hardware devices can be connected to the CPU via a system bus. The number of physical IRQs available on a system is typically limited to 16, although the IRQs can be shared or cascaded. IRQs are used to alert the CPU that an external device needs its attention and service. For example, when a key is pressed on the keyboard, an IRQ is sent to the CPU, which then sends a signal back over the IRQ line to tell the keyboard to stop sending data until the CPU reads and processes the key press.