A highly structured set of procedures that allows a user to specify certain conditions within an executing program that will result in a transfer of control from the normal program sequence to a specified routine.; 一組高度結(jié)構(gòu)化的過程,它允許用戶在一執(zhí)行中的程序內(nèi)規(guī)定某些條件,這些條件將導(dǎo)致CPU控制權(quán)從正常 程序序列轉(zhuǎn)移到某一給定例行程序。