问题
单项选择题
某文件系统中设定的物理块大小为512字节。假设一个文件控制块有48个字节，符号目录项占8字节，其中文件名占6字节，文件号占2字节；基本目录项占40字节。有一个目录文件包含256个目录项。
在进行目录项分解后，查找一个文件的平均访盘次数为（）。
A．3.5
B．6.5
C．9.5
D．12.5
答案
参考答案：A
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某文件系统中设定的物理块大小为512字节。假设一个文件控制块有48个字节，符号目录项占8字节，其中文件名占6字节，文件号占2字节；基本目录项占40字节。有一个目录文件包含256个目录项。
在进行目录项分解后，查找一个文件的平均访盘次数为（）。
A．3.5
B．6.5
C．9.5
D．12.5
参考答案：A
阅读下列短文，根据短文中的信息完成文后表格。（每空一词) In the past, man did not have to think about the protection of his environment. There were not many people on earth, and natural resources seemed to be unlimited. Today, things are different. The world has become too crowded. We are using up our natural resources too quickly, and at the same time we are polluting our environment with dangerous chemicals. If we continue like this, human life on earth will not survive. Everyone realizes today that if too many fish are taken from the sea, there will soon be none left. Yet, with modern fishing methods, more and more fish are caught. We know that if too many trees are cut down, forests will disappear and nothing will grow on the land. Yet, we continue to use bigger and more powerful machines to cut down more and more trees. We realize that if rivers are polluted with waste products from factories, we will die. However, in most countries waste products are still put into rivers or into the sea, and there are few laws to stop this. We know, too, that if the population of the world continues to rise at the present rate, in a few years, there will not be enough food. What can we do to solve these problems? If we eat more vegetables and less meat, we will easily get more food. Land that is used to grow crops can feed five times more people than land where animals are kept. The world population will not rise so quickly if people use modern methods of birth control. Finally, if we educate people to think about the problems, we shall have a better and cleaner living place in the future.
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