问题 单项选择题

由6个字符的7位ASCII编码排列,再加上水平垂直奇偶校验位构成下列矩阵 (最后一列为水平奇偶校验位,最后一行为垂直奇偶校验位)。
字符:


则X1X2X3X4处的比特分别为 (7) ;X5X6X7X8处的比特分别为 (8) ;X9X10X11X12处的比特分别为 (9)

答案

参考答案:D

解析:

[分析]: 在水平垂直奇/偶校验(方阵校验)中,最后一列为水平奇偶校验位,最后一行为垂直奇偶校验位。对于字符“+”,其水平奇偶校验位为0,而垂直奇偶校验位为0,所以 X4=0。由此也可以得出方阵校验中,水平奇偶校验和垂直奇偶校验均采用偶校验。根据这个结论,可以判断X3=1,所以X8=0,X7=0,X6=0,X5=1,X2=1,X1=1,X9=1,X10=0,X11=1,X12==1。此题的关键在于判断校验的奇偶性。

单项选择题
阅读理解

IV. 阅读理解

Bill Jenkins worked in a big office in the city, and he used to go to the barber’s during working hours to have his hair cut, although this was against the rule: clerks (职员) had to have their hair cut in their own time.

While Bill was at the barber’s one day, the manager of the office came in by chance to have his own hair cut. Bill saw him and tried to hide his face, but the manager found him.

“Hello, Jenkins,” the manager said, “ I see that you are having your hair cut in office time.”

“Yes, sir, I am,” admitted Bill calmly, “You see, sir, it grows in office time.”

“Not all of it,” said the manager at once, “some of it grows in your own time.”

“Yes, sir, but I’m not having it all cut off.”

52. Clerks in the office where Bill worked were ________.

A. not allowed to leave the office in office time

B. told to go to the barber’s in their free time

C. not allowed to go to the barber’s for a hair cut

D. told that only the manager could break the rules

53. Bill often went to have his hair cut during office hours because __________.

A. he didn’t have to wait long       B. he had no idea of the office rule

C. he couldn’t be found by the manager

D. he just wanted to save his own time to do other things

54. When the manager saw Bill at the barber’s, he was _________.

A. unhappy     B. excited       C. sad        D. anxious

55. The sentence “I’m not having it all cut off,” really means _________.

A. Bill wanted to have his hair cut, which grew in office time

B. Bill was just against the rule about hair cut

C. Bill would like to have his hair cut, which grew both in his office time and in his own time

D. Bill didn’t like to have his hair cut, which grew in his own time