Intel的CPU将特权级别分为4个级别：RING0,RING1,RING2,RING3。Windows只使用其中的两个级别RING0和RING3，RING0只给操作系统用，RING3谁都能用。如果普通应用程序企图执行RING0指令，则Windows会显示“非法指令”错误信息。-Intel' s CPU privilege level will be divided into four levels: RING0, RING1, RING2, RING3. Windows uses only one of the two levels RING0 and RING3, RING0 only to the operating system used, RING3 anyone can. If the application attempts to execute common commands RING0, Windows will display " Illegal Instruction"　error message.