When microprocessor receives interrupt signals, it sends an acknowledgement (INTA) to the peripheral which is requesting for its service. Interrupts can be classified into various categories based on different parameters: When microprocessors receive interrupt signals through pins (hardware) of microprocessor, they are known as Hardware Interrupts.

Hardware interrupt is caused by any peripheral device by sending a signal through a specified pin to the microprocessor. The 8086 has two hardware interrupt pins, i.e. NMI and INTR. NMI is a non-maskable interrupt and INTR is a maskable interrupt having lower priority. One more interrupt pin associated is INTA called interrupt acknowledge.

An interrupt is a condition that halts the microprocessor temporarily to work on a different task and then return to its previous task. Interrupt is an event or signal that request to attention of CPU. This halt allows peripheral devices to access the microprocessor.