<P> For example, a disk interrupt signals the completion of a data transfer from or to the disk peripheral; a process waiting to read or write a file starts up again . As another example, a power - off interrupt predicts or requests a loss of power, allowing the computer equipment to perform an orderly shut - down . Also, interrupts are used in typeahead features for buffering events like keystrokes . </P> <P> Interrupts are used to allow emulation of instructions which are unimplemented on certain models in a computer line . For example floating point instructions may be implemented in hardware on some systems and emulated on lower - cost systems . Execution of an unimplemented instruction will cause an interrupt . The operating system interrupt handler will recognize the occurrence on an unimplemented instruction, interpret the instruction in a software routine, and then return to the interrupting program as if the instruction had been executed . This provides application software portability across the entire line . </P>

What is meant by interrupt in operating system