问题 单项选择题

在以太帧中使用CRC校验码,其生成多项式是()。

A.G(X)=X16+X12+X5+1

B.G(X)=X16+X15+X2+1

C.G(X)=X12+X11+X3+X2+X+1

D.G(X)=X32+X26+X23+X22+X16+X12+X11+X10+X8+X7+X0+X4+X3+X+1

答案

参考答案:D

解析:

为了能对不同的错误模式进行校验,已经研究出了几种CRC生成多项式的国际标准。

CRC-CCITT G(X)=X16+X12+X5+1

CRC-16 G(X)=X16+X15+X2+1

CRC-12 G(X)=X12+X11+X3+X2+X+1

CRC-32 G(X)=X32+X26+X23+X22+X16+X12+X11+X10+X8+X7+X5+X4+X2+X+1

其中CRC-32用在以太网中,这种生成多项式能产生32位的帧校验序列。

阅读理解

阅读理解。

     "Experience may possibly be the best teacher, but it is not a particular good teacher." You might think that

Winston Churchill or perhaps Mark Twain spoke those words, but they actually come from James March, a

professor at Stanford University and a pioneer in the field of organization decision making. For years March

(possibly be wisest philosopher of management) has studied how humans think and act, and he continues to

do so in his new book The Ambiguities of Experience.

     He begins by reminding us of just how firmly we have been sticking to the idea of experiential learning:"

Experience is respected; experience is sought;experience is explained." The problem is that learning from

experience involves (涉及) serious complications (复杂化), ones that are part of the nature of experience

itself and which March discusses in the body of this book.

     In one interesting part of book, for example, he turns a double eye toward the use of stories as the most

effective way of experiential learning. He says "The more accurately (精确的) reality is presented, the less

understandable the story, and the more understandable the story, the less realistic it is."

     Besides being a broadly knowledgeable researcher. March is also a poet, and his gift shines though in the

depth of views he offers and the simple language he uses. Though the book is short, it is demanding; Don't

pick it up looking for quick, easy lessons. Rather, be ready to think deeply about learning from experience

in work and life.

1. According to the text, James March is ______.

A. a poet who uses experience in his writing

B. a teacher who teachers story writing in university

C. a researcher who studies the way humans think and act

D. a professor who helps organizations makes important decisions

2. According to James March, experience ______.

A. is overvalued

B. is easy to explain

C. should be actively sought

D. should be useless

3. What can we learn from Paragraph 3?

A. Experience makes stories more accurate.

B. Stories made interesting fail to fully present the truth.

C. The use of stories is the best way of experiential learning.

D. Stories are easier to understand when reality is more accurately described.

4. What's the purpose of this text?

A. To introduce a book.

B. To describe a researcher.

C. To explain experiential learning.

D. To discuss organizational decision making.

单项选择题 A2型题