问题 阅读理解
阅读下列短文,从四个选项中选出能回答所提问题或完成所给句子的最佳答案。
         The computer age is making an army of robots-machines that are directed by electronic (电子的) brains
and which replace human labor in industrial operations. Many are man-made arms which reach into areas man
enters only at the cost of his life, such as the inside of a nuclear reactor (核反应堆).
         Already in 1980, there were over 8000 such robots working in industrial plants throughout the world.
The big change over to the robot, however, is likely to come only when their costs go down while workers'
wages continue to rise.
1. Sentence 1 means that robots are used mainly____.
[ ]
A:to fight wars
B:to operate computers
C:to direct electronic brains
D:to take the place of human workers
2. The shape of many robots already in use looks like a human____.
[ ]
A:brain
B:arm
C:hand
D:eye
3. The passage makes it clear that a very valuable use of many robots is to _____ .
[ ]
A:act as a teacher to children
B:replace the human brain in making computers
C:help doctors in medical operations
D:do tasks very dangerous for humans to do
4. Which of the following about the last sentence is true?
[ ]
A:Robots are becoming cheaper all the time.
B:Robots are becoming more and more expensive.
C:The cost of a human worker is higher than that of the average (普通的) robot.
D:The cost of the average robot is higher than that of a human worker.
5. The writer thinks that the widespread replacement of human labor by industrial robots _____.
[ ]
A:has already begun worldwide
B:is starting especially in the developing nations
C:is being put off mainly for economic (经济的) reasons
D:will not take place before the end of this century
答案

1. D        2. B       3. D      4. D      5. C

问答题

某软件公司开发一项基于数据流的软件,其系统的主要功能是对输入的数据进行多次分析、处理和加工,生成需要的输出数据。需求方对该系统的软件可靠性要求很高,要求系统能够长时间无故障运行。该公司将该系统设计交给王工负责。王工给出该系统的模块示意图,如图5-1所示。王工解释:只要各个模块的可靠度足够高,失效率足够低,则整个软件系统的可靠性是有保证的。

李工对王工的方案提出了异议。李工认为王工的说法有两个问题:第一,即使每个模块的可靠度足够高,假设各个模块的可靠度均为0.99,但是整个软件系统模块之间全部采用串联,则整个软件系统的可靠度为0.994=0.96,即整个软件系统的可靠度下降明显;第二,软件系统模块全部采用串联结构,一旦某个模块失效,则意味着整个软件系统失效。

李工认为,应该在软件系统中采用冗余技术中的动态冗余或者软件容错的N版本程。序设计技术,对容易失效或者非常重要的模块进行冗余设计,将模块之间的串联结构部分变为并联结构,来提高整个软件系统的可靠性。同时,李工给出了采用动态冗余技术后的软件系统模块示意图,如图5-2所示。

刘工建议,李工方案中M1和M4模块没有采用容错设计,但M1和M4发生故障有可能导致严重后果。因此,可以在M1和M4模块设计上采用检错技术,在软件出现故障后能及时发现并报警,提醒维护人员进行处理。

注:假设各个模块的可靠度均为0.99。

请解释李工提出的动态冗余和N版本程序设计技术,给出图5-1中模块M2采用图5-2动态冗余技术后的可靠度。请给出采用李工设计方案后整个系统可靠度的计算方法,并计算结果。

单项选择题 案例分析题