Source : Free On-Line Dictionary of Computing

software interrupt
     
        An {interrupt} caused by a specific {machine language}
        operation code (e.g. the {Motorola 68000}'s TRAP, the {IBM
        System/390}'s SVC or the {ARM}'s SWI) rather than by a
        hardware event.
     
        As with a hardware interrupt, this causes the processor to
        store the current state, store identifying information about
        the particular interrupt, and pass control to a first level
        {interrupt handler}.
     
        A {trap} is similar except that it is caused by an unexpected
        software condition or error (e.g. divide by zero, undefined
        instruction) rather than a deliberate instruction.
     
        (1995-02-14)