问题 单项选择题

由于不同外设的工作速度一般各不相同,因此,CPU与外设交换信息时,必须确定何时从输入设备读数据以及何时往输出设备写数据,此即为输入/输出控制。下面关于PC机输入/输出控制的叙述中,正确的是( )。

A.程序控制方式是指在程序的控制下进行数据传送,这是微处理器与外部设备之向交换信息的一种最简单的方式,可分为无条件传送方式和条件传送方式两种

B.PC机输入/输出控制有三种方式:程序控制方式、中断控制方式及DMA控制方式,尽管这三种方式各有特点,但都必需通过CPU执行指令来完成具体的数据传送

C.从总体上说,中断控制方式的效率高于DMA控制方式的效率

D.一般地,中断控制方式的效率高于程序控制方式,但是,当系统有n个中断源时,CPU本身就必需有n个中断引脚,这是中断控制方式的一个缺点

答案

参考答案:A

单项选择题
阅读理解

阅读理解 (共20小题;每小题2分,满分40分)

第一节:请认真阅读下列短文,从短文后各题所给的A、B、C、D四个选项中,选出最佳选项,并在答题卡上将该项涂黑。

Skin-diving is a new sport today.

This sport takes you into a wonderful new world. It is like a visit to the moon!When you are under water,it is easy for you to climb big rocks, because you are no longer heavy.

Here,under water,everything is blue and green.During the day,there is enough light. When fish swim nearby,you can catch them with your hands.

When you have tanks(罐子)of air on your back,you can stay in deep water for a long time.But you must be careful.

To catch the fish is one of the most interesting parts of this sport.On the other hand, you can clean the ships without taking them out of the water.You can get many things from the deep sea.

Now you can see that skin-diving is both useful and interesting.

小题1:Skin-diving can take you to _______ .

A.the moon

B.mountains

C.the sun

D.the deep sea小题2:A skin-diver _______ under water in the day.

A.can see everything clearly

B.can't see anything clearly

C.can see nothing

D.can see only fishes小题3: With a tank of air on your back,you can _______ .

A.catch fish very easily

B.stay under water for a long time

C.be in safe place

D.have more fun小题4: Which of these sentences is NOT TRUE ?

A.Skin-diving is a new sport.

B.Skin-diving is like visiting the moon.

C.The only use of skin-diving is to have more fun.

D.Skin-diving is both interesting and useful.