问题 单项选择题

如图1所示为计算机中16位浮点数的表示格式。

某机器码为1110001010000000。

若阶码为移码且尾数为反码,其十进制真值为 (3)

若阶码为移码且尾数为原码,其十进制真值为 (4)

若阶码为补码且尾数为反码,其十进制真值为 (5)

若阶码为补码且尾数为原码,其十进制真值为 (6) ,将其规格化后的机器码为 (7)

(7)处填()。

A.1110001010000000

B.11110101000000

C.1101010100000000

D.11110001010000

答案

参考答案:C

解析:

本题考查计算机数据的编码,涉及原码、补码、反码,移码以及浮点数规格化处理。

同一个数可以有不同的浮点表示形式,阶码的大小可以用来调节数值中小数点的位置。将数值数据表示成/V=M*RE,M被称为N的尾数,E是N的指数或称阶码,而只是该阶码的基数。

题中阶码用4位二进制整数1110表示,尾数用12位二进制小数 001010000000表示,尾数中含有符号位,其最高位,即符号位为0。下面具体分析题目中的各个问题。

如果阶码为移码,由于阶码是4位二进制整数,设真值为X,根据整数移码定义:[X]移码=23+X(1110)2=(14)10,可求得阶码真值为 6。如果尾数为反码,从符号位可判断尾数是正数,根据小数反码定义,正小数的反码就是其自身,可求得尾数的真值为:(0.01010000000)2= (2-2+2-4)=(0.3125)10,根据浮点数定义,该机器码真值为0.3125 *26=20。

如果阶码为移码,同上,真值为6。如果尾数是原码,从符号位可判断尾数是正数,根据小数原码定义,正小数的原码就是其本身,可求得尾数的真值为0.3125。由此可知该机器码真值也是20。

如果阶码为补码,由于阶码是4位二进制整数,从符号位判断为负数,设真值为X,根据负整数定义[X]补码=24+X=(1110)2=(14)10,求得阶码的真值为-2。如果尾数为反码,同问题A-样求出尾数的真值为0.3125。这样,该机器码真值为0.3125*2-2=0.078125。

如果阶码是补码,尾数是原码,可分别参照以上解析求出阶码和尾数的真值分别为-2和0.3125,这样该机器码的真值也是0.078125。

对浮点数进行规格化处理,规定浮点数的尾数部分用纯小数形式表示,当尾数的值不为0时,其绝对值应大于或等于0.5,用二进制表示为0.1xxx…xx(x为0或1)。对于不符合这一规定的浮点数,可改变阶码的大小并同时用左右移尾数的方法来满足这一规定。显然尾数 0.01010000000不合要求,应左移1位,而阶码则应相应地减1,因此规格化处理后的阶码为1101,尾数为010100000000。

阅读理解与欣赏

阅读短文,回答问题。

狗熊

  你见过狗熊吗?它长得可好玩了。你看它,膀粗腰圆,身上长满了黑色的毛,又密又长。狗熊走起路来毛和肉一起颤动,胖得实在滑稽。它的脑袋像一个大绒毛球,上面却长着尖尖的耳朵,小小的鼻子,一对水晶球似的小眼睛。更有趣的是那条毛茸茸的小尾巴,在它身上摆来摆去,与它那肥胖的身体相比,实在不相称。

  听爷爷说,狗熊原来也有一条非常漂亮的大尾巴。因为它听了狐狸“尾巴能钓鱼”的鬼话,冬天到河边用尾巴去钓鱼,被冻在河里,猛一起身,尾巴挣断了。从此,它只剩下一条小尾巴了。多笨的狗熊呀!

  狗熊还又馋又懒。有一次,爸爸带我到动物园去玩。我一进动物园,就拿着买好的面包向养狗熊的地方跑去。我特别喜欢看狗熊敬礼,不过让它敬礼可不那么容易,只有你给它吃的,它才给你敬一个。为了逗它,我先喊:“大狗熊敬个礼!”喊了几遍它也不肯给我敬礼,还摆出一副高贵的架势。可是当我□出面包时,它的眼睛立刻紧紧地□上了面包,看上去都要□口水了。这时我挥舞着面包□它给我敬礼,它才慢慢地□起前爪在头前一摆,就算敬过礼了,□得大家直笑。等它吃完面包以后,我再叫它敬礼,它就又理也不理我了。

  你说,它哪是笨呀!

1.给文中的方框内选填正确的词语。

逗    叫  拿  流  举  盯

2.短文从哪几个方面写出狗熊“长得可好玩了”?

_______________________________________________________________

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3.“狗熊还又馋又懒”这句话在文中的作用是什么?

_______________________________________________________________

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4.用“~~”画出文中一组相互照应的句子。

5.概括本文的主要内容。

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阅读理解

My grandfather grew up in war-torn Europe. When German soldiers occupied his hometown ,the thriving city of Tarow, Poland, he refused to obey them and eventually joined the Soviet army to fight for his country’s freedom . “Stand straight, stand tall,” he told himself.

After the war, in 1947, he boarded a boat for Manhattan. He was hungry and suffering from seasickness. All alone in a new country, he was frightened about his future .Still, he marched head-on into the hustle and bustle of the streets of New York . Soon he met other European immigrants, each of them trying to find his or her own way .If they could do it, why couldn’t he? “Stand straight, stand tall,” he would remind himself.

Thanks to the help of a loyal and trusting friend, my grandfather gained a jewelry booth on Canal Street, New York City .He once told me how nervous he was on that first day of work. He was not only trying to learn this tough new business, but also a new language.

To his surprise, the men in neighboring booths—who could have taken advantage of him—offered their help and advice. Within months, my grandfather was commanding his spot behind the counter, selling diamonds and cultured pearls as if he’d been doing it his whole life.

Stand straight and stand tall.

In later years, my grandfather would take both my mother and her sister down the aisle at their weddings. As he stood with each of them, he thought about their new beginnings, and of the adventures and journeys they would experience together .He also thought about the children who would one day carry on his family name.

I am so proud to be one of those children. Listening to my grandfather’s remarkable experiences has changed the way I view my own life.

56.Which is the correct order of the things that happened in the passage?

a. My grandfather took both my mother and her sister down the aisle at their weddings.

b. World War II broke out in Europe.

c. My grandfather went to America.

d. My grandfather began to run his diamond business.

e. The men in neighboring booths helped him.

A.b, c, a ,d, e          B.b, c,d ,e ,a           C.b, c ,e , a ,d        D.c, b ,e ,d ,a

57.Which is NOT true according to the passage?

A.My grandfather was a soldier during World War II.

B.My grandfather went to America by sea.

C.My grandfather had been doing a jewelry business his whole life.

D.My grandfather ran his business successfully.

58.Grandpa probably inspired his grandchildren in time of trouble by saying “    ”.

A.A friend in need is a friend indeed

B.God help those who help themselves

C.Stand straight ,stand tall

D.Practice makes perfect

59.It can be concluded that    .

A.Grandpa never lost heart in time of hardships

B.Grandpa never threw doubt upon his fate

C.Grandpa was born to be a businessman

D.Grandpa didn’t live up to his friend’s expectations