2013年计算机等级四级考试笔试模拟试题三

　　(71) In order to append a standard output to an existing file, which of the following operators is used in the UNIX system? ____.

　　A) | B) & C) > D) >>

　　(72) Consider the following figure, where the shaded parts represent already assigned blocks of memory, and the unshaded parts represent free blocks. (2分) If there is a request for 40KB of memory and the best-fit algorithm is used, then the beginning address of memory that is allocated in response to the request is ____. 　　　　　 　A) 100KB B) 190KB C) 330KB D) 410KB

　　(73) On a certain disk, there are 200 tracks, numbered 0-199, the current position of the disk head is track 53. If the shortest-seek-time-first scheduling algorithm is used when the tracks

　　98, 183, 37, 122, 14, 124, 65, 67

　　are requested, then the head-moving sequence that results will be (2分)

　　A) 65, 67, 37, 14, 98, 122, 124, 183

　　B) 65, 67, 37, 98, 122, 124, 183, 14

　　C) 65, 67, 98, 122, 124, 183, 37, 14

　　D) 98, 183, 37, 122, 14, 124, 65, 67

　　(74) Whant operation on relations R and S produces the relation shown below?____.

　　{tuple│tuple∈R۸tuple∈\ S}

　　A) Union B) Difference C) Intersection D) Division

　　(75) When embedding SQL in a C language program, the prefix that should be added to all SQL statements in order to distinguish SQL statements from the host language statements is____.

　　A) ： B) EXEC C) EXEC SQL D) SQL

　　(76) In the ORACLE system,sets of SQL statements and control flow statements that have been named,compiled,and stored tn the database are referred to as stored____.

　　A) batches B) procedures C) triggers D) transactions

　　(77) Which of the following statements about object oriented databases is NOT correct? ____. (2分)

　　A) Each object has a unique object identity in the system.

　　B) Encapsulation and inheritance are two important features of object oriented databases.

　　C) A subclass can inherit the attributes and methods of all its superclasses.

　　D) A superclass includes the attributes and methods of all its subclasses.

　　(78) In the design phase of software engineering, decomposition of the program into modules should follow the principles of ____.

　　A) low cohesion with low corpling 　　B) low cohesion with high coupling

　　C) high cohesion with low coupling 　D) high cohesion with high coupling

　　(79) Specifications for software should contain&nbs p;several components, e.g., specifications of

　　information flow,

　　user interface,

　　functional requirements, and

　　design constraints.

　　Two other important components are specifications of the____. (2分)

　　A) methods of testing and ways to obtain quality assurance

　　B) criteria for testing and ways to obtain quality assurance

　　C) methods of testing and criteria for function assurane

　　D) criteria for testing and methods of function assurance

　　(80) Which of the following statements about testing software with data is (are) true?____.

　　I. The primary purpose of such testing is to find errors.

　　II. Such testing can demonstrate the existence of errors but cannot

　　demonstrate the absence of errors.

　　A) Neither B) Ⅰ only C) Ⅱ only D) Ⅰ and Ⅱ

　　(81) The type of testing done during software implementation and beforemodule integration is called ____.

　　A) unit testing B) beta testing

　　C) system testing D) acceptance testing

　　(82) Which of the following is (are) true about software portability? ____.

　　I. Using a high-level language that conforms to an ISO standardguarantees portability across the range of machines that support the language.

　　II. Portability is guaranteed across all machines that have the same instruction set and operating system. (2分)

　　A) Neither B) Ⅰ only C) Ⅱ only D) Ⅰ and Ⅱ

　　(83) A memory-memory, machine instruction for a certain machine has the following format.

　　(Such an instruction is similar to a register-register instruction

　　except that the operands are displaced addresses in memory.)

　　opcode meml displ1 mem2 displ2

　　Which of the following could be an assembly lanuage instruction that would be translated into a memory-to-memory instruction for this machine? ____.

　　A) ADD 10(R1), 20(R2) B) ADD(10R1), (20R2)

　　C) ADD R1, 10(R2), 20 D) ADD R1, 10, 20(R2)

　　(84) In a certain cache system, the modified cache block is written to main memory only when the block is replaced. All of the following are used to describe this policy EXCEPT____.

　　A) store-in B) write-back C) copy-back D) write-through

　　(85) When an amount of memory is requested that is less than the size of a page, but a full page is allocated, the r esulting waste of memory is called ____.

　　A) external fragmentation B) internal fragmentation

　　C) inaccessible page faults D) inaccessible garbage

　　(86) The time that the CPU spends on a given program can be computed using all of the following expressions EXCEPT ____. (2分)

　　A) (CPU clock cycles for the program)*(clock cycle time)

　　B) CPU clock cycles for the program

　　clock rate

　　C) (Instruction count)*CPI

　　clock rate

　　D) (CPU clock cycles for the program)*CPI

　　clock rate

　　(87) The methods used in Asynchronous Transfer Mode (ATM) are switch technology and which of the following is used to describe this mode?____.

　　A) cell exchange B) packet exchange

　　C) message exchange D) information exchange

　　(88) In a data communication system, the transport media with the widest frequency band and best reliability is the ____.

　　A) telephone line B) coaxial cable

　　C) radio channel D) fiber optic cable

　　(89) Which of the following statements about the Internet is (are) true?____.　　　 I. It is possible to have multiple names corresponding to the same IP address. II. All host names must be registered with an Internet-wide central registry.

　　A) Neither B) Ⅰ only C) Ⅱ only D) Ⅰ and Ⅱ

　　(90) According to the principle of CRC calculation, given a frame-bit series M =11100111 and the multiple-term formula, frame-bit series generated by the CRC G =110011, then the CRC is ____.(2分)

　　A) 111101 B) 00011 C) 11010011 D) 1101001

　　二、论述题(两个论述题可任选其一,并只选其一,多选无效,满分30分。)

　　论述题 1

　　局域网是当前计算机网络研究与应用的一个热点,而符合IEEE 802.3标准的传统Ethenet(MAC层采用CSMA/CD方法,物理层采用 10BASE-T标准)应用最为广泛。随着网络应用的发展,以及大型信息系统与多媒体技术的应用,人们对局域网性能提出了越来越高的要求,出现了符合 100BASE-T标准的Fast Ethernet、交换局域网Switching LAN与ATM等高速局域网产品。尽管高速局域网技术发展十分迅速,但是Ethernet仍然会被广泛地使用。今后的网络应该是传统Ethernet、FastEthernet LAN与ATM共存的结构。因此,研究 Ethernet的基本工作原理、优点与缺点,讨论高速局域网络发展的趋势与特点,对我们学习和掌握局域网应用技术是十分重要的。

　　(1) 请用Ethernet发送与接收流程框图说明CSMA/CD介质访问控制方法的基本工作原理。(15分)

　　(2) 为什么说CSMA/CD属于共享介质、随机争用型的介质访问控制方法?这种方法主要缺点是什么? (5分)

　　(3) 你认为Fast Ethernet与ATM、Switching LAN是从哪两个方面改进了传统的Ethernet?它们各有什么优缺点? (10分)

　　论述题 2

　　进程通信就是进程之间进行信息交换。系统中各进程异步执行,但有些进程之间必须保持一定的联系,以便协调一致地完成指定任务。这种联系就是通过交换一定数量的信息来实现的。

　　消息缓冲通信技术是一种高级通信机制,由Hansen首先提出。其基本思想是:根据"生产者-消费者关系"原理,利用公共消息缓冲区实现进程之间的信息交换。

　　(1) 试叙述高级通信机制与低级通信机制P、V原语操作的主要区别。(5分)

　　(2) 试叙述解释消息缓冲通信技术的基本原理。 (10分)

　　(3) 消息缓冲通信机制中提供发送消息原语。Send(receiver,a)和接收消息原语Receive(a)。调用参数a分别表示发送消息的内存区首地址或接收进程的内存消息区首地址。试设计相应的数据结构,并用P、V操作原语实现Send和Receive原语。 (15分)

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