问题 单项选择题

数据库中为了将大小不同的记录组织在同一个磁盘块中,常采用分槽的页结构。结构的块头中不包括( )。

A.块中记录的数目

B.读取时需要的缓存大小

C.块中空闲空间的末尾指针

D.由包含记录位置和大小的条目组成的数组

答案

参考答案:B

解析: 按分槽的页结构组织变长记录,在每个块的开始处的块头中记录有如下信息:块头中记录条目的个数、块中空闲空间的末尾地址、一个包含每条记录位置和大小的条目组成的数组。没有读取时需要的缓存大小等信息,所以正确答案选B。

阅读理解

When the TV viewer turns on his set, what sort of programs does he have to choose from? You might think there would be more programs devoted to entertainment than to anything else, but that’s not the case. In most countries, fewer than 20% of broadcasting hours are devoted to entertainment. U.S. figures are high----34.8% , and the unloving Canadians are even higher with 44%. Except Canada and Italy, all countries give more broadcasting time to education than to either information (news , documentaries and so on) or entertainment programs. Of course, few educational broadcasts take place during peak viewing times. In Japan though , more than 60%of broadcasting time is taken up with education of one kind of anther----just another example of the businesslike Japanese philosophy. In the U.K., the figure is 56.4% . the Italians have fewer educational programs than anyone else. They don’t go in for entertainment either. Only about ten percent of viewing time is devoted to dramas and serials, quiz shows, music, sports etc. You will find more news information programs on Italian TV than anything else. That’s understandable in a country experiencing social and political changes. Italians rely on TV to tell them what’s going on---and events are happening almost too fast to follow. The percentage of time the U.S. devoted to news and documentary programs is much smaller. After education, most TV time is given to entertainment. Many of these programs are shown around the world.

小题1:Based on this passage, the greatest percentage of TV broadcasting hours to educational is in __.

A.Japan

B.Italy

C.Canada

D.the United States小题2:More news information programs are broadcast on Italian TV than anywhere else because the Italians ___.

A.are interested in what is happening in the world.

B.Like to follow the changes that are going on in their social life

C.Prefer to learn news information on TV rather than in newspapers

D.Expect TV to tell them the latest news about what is going on in their country小题3: So far as the broadcasting hours devoted to entertainment , which of the following is true?

A.The Japanese figure is the highest in the world.

B.The U.S. figure is smaller than the U. K. figure

C.The U.K. figure is second to the Japanese figure

D.The Canadian figure is higher than that of any other country.小题4:In the United States, ____.

A.TV programs are shown for world audience to watch

B.Most of TV broadcasting hours are give to entertainment

C.Educational programs are shown during peak viewing times

D.TV broadcasting hours devoted to education are more than those devoted to entertainment

单项选择题