What is to interrupt? In showing the computer runs a course, appear when certain and accident circumstance needs lead plane to intervene, the program that the machine can suspend automatically to moving turns into the order that handles new case, the program that is suspended formerly is returned to continue to move again after processing ends. (the standard defines) interrupt a function: ① improves efficiency of all of computer science department. The working rate of the peripheral equipment of working rate outclass of the processor in all of computer science department. Can coordinate the work between them through interrupting. ② maintains a system to work normally reliably. Programmer cannot intervene directly and operate machine, must issue a request to the operating system through breaking a system, will realize factitious interpose by the operating system. ③ satisfies real time to handle a demand. In real time system, all sorts of monitoring and control equipment is given out randomly to processor suspend a request, processor is answered at any time and undertake handling. ④ offers trouble spot to handle an instrument. The part that all sorts of breakdown detect and the mistake diagnoses is set in processor, once discover breakdown or error, give out instantly suspend a request, undertake breakdown the spot is recorded and be kept apart, provide necessary basis for further processing. Interrupt lien: When some quarter have a few to interrupt a source to be given out at the same time when suspending a request, processor is answered only among them lien interrupts a source highestly. Moving when processor a certain when another request that suspends a source appearing during suspending service program, if latter lien under former, processor does not grant pay attention to, conversely, processor answers latter instantly, enter so called " nest is interrupted " . Interrupt processing process: ① interrupts a source to give out suspend a request; ② judges current processor to whether allow to interrupt and should interrupt a source whether by screen; ③ lien queues up; ④ processor carries out current statement or current statement cannot be carried out, suspend current program instantly, protective breakpoint address and processor are current condition, turn to suspend service program accordingly; ⑤ is carried out suspend service program; ⑥ regains the position that is protected, carry out " interrupt return " the instruction is returned the program that is suspended or turn into other program. Before afore-mentioned processes are medium 4 operations are completed by hardware, hind two are finished by software. CNC MillingCNC Machining