2019年全国计算机等级考试四级模拟试题及答案7

1、2019 年全国计算机等级考试四级模拟试题及答案 7(61) There are several periods in a computer，the shortestperiod isAInstruction periodB Machine periodCBeat periodDCPU period(62) Which set is empty?A. xx is a real nu mber and x2=9 B) xx is a real nu mber and x2-1=0C) xx is a real number and x2+1=0 D) xx is a real numberand

2、 x=2x+1 (63) What is the relation represented in the exhibit shown below?A. R=(1,2),(1,3),(1,4),(1,5)B. R=(1,1),(2,2),(3,3),(4,4),(5,5)C. R=(1,2),(1,3),(1,4),(2,3),(4,1),(4,5),(5,5)D. R=(1,2),(1,3),(1,4),(2,2),(2,3),(4,1),(4,4),(4,5)(64) What is the contrapositive of the followingimplication? “ If i

3、t is raining , then I get wet. ”A.If I get wet ，then it is raining.B If I am wet ，then if is raining.C If it is not raining, I do not get wet.D If I do not get wet，then it is not raining.(65) Which property does R posses? (2 grades)Let A=1,2,3,4 and let R =,A SymmetryB ReflexivityC AsymmetryD Antisy

4、mmetry(66) When walking a tree, which traversal method yields a prefix, or Polish,form?A lnorderB PreorderCPostorderD Reorder(67) ln the following statements about graph operations, which one is NOT correct?(2 grades)A Spanning tree of a graph may not be unique.B Minimum spanning tree of a graph may

5、 not be unique.C Finding critical path is an operation on directed graph.D Finding critical path is an operation on undirected graph.(68) Which traversal method for a binary tree does the following Pascal code illustrate? (2 grades) procedure traverse(p ：pointer);beginif p(69) What storage scheme do

6、es MS-DOS use for storing files on a disk?AI-nodesB a linked list allocationC a continuous allocationD a linked list with index(70) Which of the followings is NOT a condition for deadlock?AStarvationB Circular WaitC No PreemptionD Mutual Exclusion(71) Assume that an operating system uses a round-rob

7、in scheduler. The process s quantum is 20 msec,and the context switch is 5 msec. What percentage of the CPUs time is spenton administrative overhead? (2 grades)A5B15C20D25(72) What state is a process in when it cant runbecause it needs a resource to become available? (2 grades) AReadyBInterruptCBloc

8、kedD Running(73) The following sectors are requested from the disk 11,1,36,16,34,9,12What is the order of the sector reads if you are using the elevator algorithm?(2 grades)A1,9,11,12,16,34,36B11,1,36,16,34,9,12C11,12,9,16,1,34,36D11,12,16,34,36,9,1(74) What is the candidate key of a relational data

9、base?A A field with a constraint placed on it.B A set of fields that have no data in them.C A set of fields in a table used to identify a record uniquely.D Fields from multiple tables that are used for sorting records.(75) What Normal From is the table shown in the exhibit? (2 grades) emps tblemp_id

10、emp_nameemp_phonedept_namedept_phonedept_mgrname(1) emp_id emp_ name, empph one, dept_ name(2) dept_ namA dept_pho ne, dept_mgr nameA 1NFB2NFC3NFDBCNF(76) Which operating system can Oracle database NOT be used in?ADOSBUNIXC Wi n d ows95DIBM Mainframes(77) Which values are NOT permitted to be part of

11、 the primary key?ANULLBpunctuationCspecial charactersDalpha-numeric characters(78) Which phase of the software engineering process results in the Software Requirements Specification?A definition phaseB engineering phaseC maintenance phaseD development phase(79) When drawing multilevel data flow char

12、t of top-down, the balance between parent chart and son chart must be taken into account, and to pass judgment for the balance of the charts is regularly maintained by (2 grades)A Output dataB Data dictionaryC Processing numberD Input data(80) Which is the strictest form of cohesion?AlogicalB functi

13、onalCproceduralDcoincidental(81) Which is NOT a concept of White Box Testing? (2 grades)A You should execute all loops at their boundary conditions.B You should execute all interfaces at their boundary conditions.C You should execute all logical decisions on their true and false sides.D You should e

14、xecute all independent paths within a module at least once.(82) Prototyping method is a dynamic design process, it requires people who use prototyping method should have the following capabilityA Proficient program expertiseB Immediately acquire requirementC Coordinate & organize eloquentlyD Handle

15、tools smartly(83) There are two styles in the evolution of instruction set , that is CISC and RISC. Which chip belongs to the RISC?A i APX 432BVAX-11/780C Motorola 68000D Power PC(84) In advanced PC bus or local bus, which one has the fastest data throughput?AISABPCICMCADEISA(85) There are many meth

16、ods in the CPETT(short for Computer Performance Evaluation Tools and Techniques). One of them is the method that runs a Kernel as the load of a computer. So we call itA Monitor methodB Benchmark methodC Model methodD Physical method(86) There are two common types in page replacement algorithm ： stac

17、k and non-stack strategies. When a real page number increase only stack algorithm can increase the hit rate monotonously. In the following replacement algorithm,which one belongs to non-stack strategy?(2 grades) AFIFOBLRUCPFFDOPT(87) What binary number is encoded with Differential Manchester in the

18、diagram below? (2 grades)A10110011100B11001100011C11000110010D00111001101(88) Each host or router on the Internet has its own IP address. There are four IP addresses as followings. Which IP address is erronedus?A189.132.2.1B255.255.255.0C198.73.265.50D192.0.0.3(89) When should Frequency Division Multiplexing be used? A when the attenuation on a medium is greater than 25.B when the white noise on the medium exceeds 50 of themediums bandwidthC whe