2022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 shortest period is AInstruction period BMachine period CBeat period DCPU period /PP (62) Which set is empty? Axx is a real number and x2=9 B)xx is a real number and x2-1=0 C)xx is a real number and x2+1=0 D)xx is a real number and x=2x+1 /PP (63) What is the relation represented in the exhibit shown below? AR=(1,2),(1,3),(1,4),(1,5) BR=(1,1),(2,2),(3,3),(4,4),(5,5) CR=(1,2),(1,3),(1,4),(2,3),(4,1),(4,5),(5,5) DR=(1,2),(1,3),(1,4),(2,2),(2,3),(4,1),(4,4),(4,5) /PP (64) What is the contrapositive of the following implication?“If it is raining，then I get wet.” AIf I get wet，then it is raining. BIf I am wet ，then if is raining. CIf it is not raining, I do not get wet. DIf I do not get wet，then it is not raining. /PP (65) Which property does R posses? (2 grades) Let A=1,2,3,4 and let R =1 2=,2 2=,3 4=,4 1= ASymmetry BReflexivity CAsymmetry DAntisymmetry /PP (66) When walking a tree, which traversal method yields a prefix, or Polish,form? Alnorder BPreorder CPostorder DReorder/PP (67) ln the following statements about graph operations, which one is NOT correct? (2 grades) ASpanning tree of a graph may not be unique. BMinimum spanning tree of a graph may not be unique. CFinding critical path is an operation on directed graph. DFinding critical path is an operation on undirected graph. /PP (68) Which traversal method for a binary tree does the following Pascal code illustrate? (2 grades) procedure traverse(p:pointer); begin if pnil then begin traverse(p.left); process(p); traverse(p.right) end end; Alnorder BPreorder CPostorder DReorder /PP (69) What storage scheme does MS-DOS use for storing files on a disk? AI-nodes Ba linked list allocation Ca continuous allocation Da linked list with index /PP (70) Which of the followings is NOT a condition for deadlock? AStarvation BCircular Wait CNo Preemption DMutual Exclusion /PP (71) Assume that an operating system uses a round-robin scheduler. The processs quantum is 20 msec,and the context switch is 5 msec. What percentage of the CPUs time is spent on administrative overhead? (2 grades) A5 B15 C20 D25 /PP (72) What state is a process in when it cant run because it needs a resource to become available? (2 grades) AReady BInterrupt CBlocked DRunning /PP (73) The following sectors are requested from the disk: 11,1,36,16,34,9,12 What is the order of the sector reads if you are using the elevator algorithm? (2 grades) A1,9,11,12,16,34,36 B11,1,36,16,34,9,12 C11,12,9,16,1,34,36 D11,12,16,34,36,9,1 /PP (74) What is the candidate key of a relational database? AA field with a constraint placed on it. BA set of fields that have no data in them. CA set of fields in a table used to identify a record uniquely. DFields from multiple tables that are used for sorting records. /PP (75) What Normal From is the table shown in the exhibit? (2 grades) /PPemps tbl emp_idemp_nameemp_phonedept_namedept_phonedept_mgrname (1) emp_idemp_name, emp_phone, dept_name(2) dept_namedept_phone, dept_mgrname A1NF B2NF C3NF DBCNF /PP /PP (76) Which operating system can Oracle database NOT be used in? ADOS BUNIX CWindows95 DIBM Mainframes /PP (77) Which values are NOT permitted to be part of the primary key? ANULL Bpunctuation Cspecial characters Dalpha-numeric characters /PP (78) Which phase of the software engineering process results in the Software Requirements Specification? Adefinition phase Bengineering phase Cmaintenance phase Ddevelopment phase /PP (79) When drawing multilevel data flow chart 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) AOutput data BData dictionary CProcessing number DInput data /PP (80) Which is the strictest form of cohesion? Alogical Bfunctional Cprocedural Dcoincidental /PP (81) Which is NOT a concept of White Box Testing? (2 grades) AYou should execute all loops at their boundary conditions. BYou should execute all interfaces at their boundary conditions. CYou should execute all logical decisi