序幕先于较重要部分的介绍性表演，事件或行动；开端或序 An introductory performance, event, or action preceding a more important one; a preliminary or preface.
指实现后台处理。所谓后台处理是指非联机处理，或者说不是直接和计算机连接起来而进行联机操作。优先级高的程序先于特定的后台作业执行。 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.
约翰一直领先于其他赛手，并最后赢得冠军。 John kept ahead of the other runners and won at last.
