指實現後台處理。所謂後台處理是指非聯機處理，或者說不是直接和計算機連接起來而進行聯機操作。優先順序高的程序先於特定的後台作業執行。
Performing background processing which is not on-line or directly connected to the computer for on-line operation. High priority programs take precedence over specific background jobs.
一種重要的處理過程，其中最高優先權處理任務常常由具有優先度的實時任務形成，經過使用中斷而進入較低優先權任務或後台處理任務。
An important processing procedure in which top-priority processing most often results from real-time entries which usually have precedence, through the use of interrupts into lower-priority or background processing.
