全国计算机等级考试四级笔试试题(一)7

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　　(80) Which of the following statements about testing software with data is (are) true
; h1 V, K0 u( M" z7 V　　I. The primary purpose of such testing is to find errors.
0 [8 n/ `% S2 p' Q( k　　II. Such testing can demonstrate the existence of errors but cannot
　　demonstrate the absence of errors.
- M/ H) O' \2 Q* i　　A) Neither B) Ⅰ only C) Ⅱ only D) Ⅰ and Ⅱ
+ N4 D3 s. l/ |& C+ `　　(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
% c1 |  n  G$ A% ~0 s/ T. S! b　　(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.
6 E# t8 e3 [; p/ V9 I　　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.
4 V" X3 J$ b1 r* s$ a$ D& m　　(Such an instruction is similar to a register-register instruction
% d) p& ~+ }( L) f　　except that the operands are displaced addresses in memory.)
7 o2 A. q0 {- {* ~2 L4 e* @$ f　　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
; ]* Z/ z- r% G1 E4 M2 q* J　　A) ADD 10(R1), 20(R2) B) ADD(10R1), (20R2)
　　C) ADD R1, 10(R2), 20 D) ADD R1, 10, 20(R2)
1 s* U: h! X4 u0 P$ s1 {  J% t　　(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
/ C! n- g, C- P; U6 D　　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
: ?; N7 a" ?5 U& v3 c  w9 K　　C) inaccessible page faults D) inaccessible garbage
7 ~* M. T$ l$ `% ^1 |& X9 t　　(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)
( ^7 N1 p9 `7 Z* ~% s　　B) CPU clock cycles for the program
8 G) B5 T7 G9 y/ k; y　　clock rate
- Z8 s$ y) _0 f: ^; T3 ~" G　　C) (Instruction count)*CPI
　　clock rate
　　D) (CPU clock cycles for the program)*CPI
0 I! d6 f" c! r' K5 w2 s* H9 l　　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
2 e5 i* p. @# e6 {　　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
5 ?) B  y  V6 y$ T; u　　A) telephone line B) coaxial cable
　　C) radio channel D) fiber optic cable
0 K" ]' L" F% s% Z0 J& A$ c+ V　　(89) Which of the following statements about the Internet is (are) true
# n4 g) A& T2 H; Q4 R1 w& z8 V　　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.
0 B; \9 x- O0 _; i2 A1 n　　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)
4 U. Z% x6 {7 ^. @0 V8 V+ J3 v　　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
; i# U3 r' |) i9 v　　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)
' O: k5 L% N. E9 Z& U) g　　(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)
; \9 ]! d# w: u, S　　(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)

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　　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。
: t2 Q1 }& o6 h5 {) |' C  L4 t　　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)
* h* U& H7 v& T( z9 E6 O4 ?　　(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)