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全国计算机等级考试四级笔试试题一（下）
(51) 在OSI参考模型中,同等层相互交换信息的实体构成了____。A) 相邻实体 B) 对等实体 C) 传输实体 D) 通信实体
(52) 在OSI参考模型中,两个(N)层实体之间交换的数据单元称之为(N)协议数据单元,记做(N)PDU。(N)PDU是由两部分组成:(N)PCI与 ____。
A) (N+1)IDU B) (N+1)SDU C) (N)SDU D) (N)IDU
(53) 一个数据源产生8bit的ASCII字符(含1bit校验位),通过一条64Kbps的线路进行数据传输。指出在以下数据传输方式中,哪一种方式的有效数据传输速率可以达到最高? ____。(2分)
A) 采用面向字符型传输协议,每个数据帧包括24B的控制字段与128B的信息字段
B) 除信息字段长度为256B外,其它条件同A)
C) 采用面向比特型传输协议,每个数据帧包括12B的控制字段与64B的信息字段
D) 除信息字段长度为128B外,其它条件同C)
(54) 在面向比特型数据链路层协议HDLC中,帧格式中的哪个域既可以用于流量控制,又可以实现对发送帧的捎带确认?____。（2分）
A) 无编号帧的M域 B) 信息帧的N(S)域
C) 监控帧的S域 D) 信息帧的N(R)、N(S)域
(55) IEEE802.5标准规定令牌环网采用 ____。
A) 多令牌协议
B) 单令牌协议
C) 随机访问协议
D) HDLC协议
(56) 在局域网中,以下哪种传输介质既可以用于物理层10BASE-T协议,又可以适用于100BASE-T协议? ____。
A) 同轴电缆 B) 3类非屏蔽双绞线
C) 5类非屏蔽双绞线 D) 光纤电缆
(57) 如果两个局域网LAN A与LAN B互连,它们的传输层协议不同,而其它层协议均相同, LAN A与LAN B的互连设备应该选择____。
A) repeater B) bridge C) router D) gateway
(58) CCITT推荐的用于多个X.25网络互连的协议为____。
A) X.400 B) X.75 C) X.121 D) X.21
(59) 城市地区网(MAN)主要使用的技术是交换多兆位数据服务SMDS、分布队列双总线DQDB和____。
A) FDDI B) CSMA/CD C) Token Bus D) Token Ring
(60) 在计算机集成制造系统(CIMS)中,存在着办 公自动化(OA)与生产过程控制(MC)两种环境,它们对网络通信的要求也不相同。在CIMS环境中,根据MAP/TOP协议选择局域网协议标准时，应采用以下哪种方案? ____。(2分)
A) 全部采用802.3协议标准
B) OA采用802.3协议标准,MC采用802.4协议标准
C) OA采用802.3协议标准,MC采用802.5协议标准
D) 全部采用HDLC协议标准
(61) An instrucion that uses indirect addressing must contain an address of memory where____．
A) data is stored B) another address is stored
C) a page fault is addressed D) a pepeline stall will be executed
(62) Let R be a binary relation on a set S such that for each x,y,z∈S, if xRy and xRz then y =z. Which of the following must be true? ____．(2分)
A) R is anti-symmetric B) R is transitive
C) R is an equivalence relation D) R is a function
(63) If p and q are Boolean variables, which of the following formulas is (are) tautological?____．
Ⅰ. (┐p→q)↔ (p∨q)
Ⅱ. ((p→q))∧(q→r))→(p→r))
A) none B) Ⅰ only C) Ⅱ only D) Ⅰ and Ⅱ
(64) Which of the following statements is (are) true? ____．
Ⅰ. The number of cyclic subgroups of the additive group of integers is infinite.
Ⅱ. The number of cyclic subgroups of the additive group of real numbers is infinite.
A)&nb sp;Neither B) Ⅰ only C) Ⅱ only D) Ⅰ and Ⅱ
Questions 65- 66 refer to the space requirements of different methods of storing graphs. The choices for these questions are combinations of the following statements.
Ⅰ. The space required depends on the number of vertices.
Ⅱ. The space required depends on the number of edges.
(65) When the adjacency matrix method is used to store a graph, which of the statements is (are) true? ____．
A) None B) Ⅰ only C) Ⅱ only D) Ⅰ and Ⅱ
(66) When the adjacency list method is used to store a graph, which of the statements is (are) true?____．
A) None B) Ⅰ only C) Ⅱ only D) Ⅰ and Ⅱ
Questions 67-68 are based on the following information,
A hash table with hash function
h1(k)=k mod 13
is shown below.
0 1 2 3 4 5 6 7 8 9 10 11 12
35 33 48 25
Collision is resolved using the hash function h2(k)=(k mod 11)+1.
(67) How many key comparisons occur in searching for key 35 in the given hash table?____． (2分)
A) 0 B) 1 C) 2 D) 3
(68)& If a new key 67 is inserted into the given hash table, what will be its address?____． (2分)
A) 3 B) 4 C) 5 D) 6
(69) Suppose the contents of the DOS IF1.BAT file on the hard disk is as follows.
@ECHO OFF
MEM>FILE1
SORTFILE2
DEL FILE1
@DATE
@TIME
IF EXIST %1 ECHO % IF FOUND
If all of the commands are successfully executed after IF1 FILE1 is
typed, then the screen displays?____．
A) None B) Date and time C) FILE1 IS FOUND D) FILE2 IS FOUND
(70) If the files in the current directory are
aac, abc, acb,acc, aca, ao, al, a2, ab, ac, aa,
and the command ls a?[bc] is executed, how many files will be listed?____． (2分)
A) 3 B) 4 C) 5 D) 6
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