某仓库有两名发货员，一名审核员。当顾客提货时，只要发货员空闲，允许顾客进入仓库提货，顾客离开时，审核员检验顾客提货是否正确。其工作流程如图13-15所示。为了利用PV操作正确地协调他们之间的工作，设置了两个信号量S1和S2，且S1的初值为 2，S2的初值为1。图中的a应填写(54)；图中的b、c和d应分别填写(55)。

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XP is (71) of interesting twists that encourage one to think--for example, how about "Test and then code"? I've worked with software companies and a few IT organizations in (72) programmer performance was measured on lines of code delivered and testing was measured on defects found-- (73) side was motivated to reduce the number of defects prior to testing. XP uses two types of testing: unit and functional. (74) , the practice for unit testing involves developing the test for the feature prior to writing the code and further states that the tests should be automated. Once the code is written, it is immediately (75) to the test suite bringing instant feedback.

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MPEG-4是(53)，MPEG-4主要由音频编码、视频编码、数据平面、(54)、缓冲区管理和实时识别等部分构成，其中数据平面包括(55)两部分。

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