Q. Define Interrupts in assembly language?

An interrupt causes interruption of an ongoing program. A number of the common interrupts are: printer, monitor, keyboard, an error condition and trap etc. 

8086 identifies two types of interrupts: Software interrupts and Hardware interrupts.

Hardware interrupts are produced when a peripheral Interrupt servicing program requests for some service. A software interrupt causes a call to OS. It generally is the input-output routine. 

Let's discuss software interrupts in more detail. A software interrupt is started using following statements:

INT number

In 8086 this interrupt instruction is processing employing the interrupt vector table (IVT). The IVT is situated in the first 1K bytes of memory and has a total of 256 entities every one of them of 4 bytes. An entry in interrupt vector table is recognised by the number provided in the interrupt instruction. Entry stores the address of operating system subroutine which is used to process interrupt. This address can be different for numerous machines. Figure belowdisplays the processing of an interrupt.

Figure: Processing of an Interrupt