有一活动头的磁盘系统，磁盘块地址用一个三元组＜x，y，z＞来表示，其中，x代表柱面号，y代表磁盘面号，z代表扇区号。现有一组使用磁盘的申请，其磁盘访问地址依次为＜100,12,6＞，＜35，18,4＞，＜20．4,10＞，＜32,8,12＞，＜45，8，6＞，＜120,4,12＞，＜15，7，6＞。系统实际响应的磁盘访问序列为＜32,8,12＞，＜35,18,4＞，＜45，8，6，＞＜100,12,6＞，＜120,4,12＞，＜20.4,10＞，＜15，7，6＞。本系统采用的磁盘调度算法是(26)。

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Software　design　is　a(71)process　.It　requires　a　certain(72)of　flair　on　the　part　of　the　designer.　Design　can　not　be　learned　from　a　book　.It　must　be　practiced　and　learnt　by　experience　and　study　of　existing　systems　.A　well(73)software　system　is　straightforward　to　implement　and　maintain　,easily(74)and　reliable　.Badly(73)software　systems　,although　they　may　work　are(75)to　be　expensive　to　maintain　,difficult　to　test　and　unreliable.

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(66)is a protocol that a host uses to inform. a router when it joins or leaves an Internet multicast group.

(67)is an error detection code that most data conlmunication networks use.

(68)is an interior gateway protocol that uses a distance vector algorithm to propagate routing information.

(69)is a transfer mode in which all types of information are organized into fixed form. cells on an asynchronous or nonperiodic basis over a range of media.

(70)is an identifier of a web page.