2021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 计算机四级考试内容
A．Instruction period
B．Machine period
C．Beat period
D．CPU period </P><P>
  (62) Which set is empty?
A．｛xx 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｝ </P><P>
  (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)} </P><P>
  (64) What is the contrapositive of the following implication?“If it 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. </P><P>
  (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="">}
A．Symmetry
B．Reflexivity
C．Asymmetry
D．Antisymmetry </P><P>
  (66) When walking a tree, which traversal method yields a prefix, or Polish,form?
A．lnorder
B．Preorder
C．Postorder
D．Reorder</P><P>
  (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 not be unique.
C．Finding critical path is an operation on directed graph.
D．Finding critical path is an operation on undirected graph. </P><P>
  (68) Which traversal method for a binary tree does the following Pascal code illustrate? (2 grades)
procedure traverse(p:pointer);
begin
if p<>nil 网上银行
then begin
traverse(p↑.left);
process(p);
traverse(p↑.right) 国考成绩发布在即
end
end;
A．lnorder
B．Preorder 四川省公务员考试网
C．Postorder
D．Reorder </P><P>
  (69) What storage scheme does MS-DOS use for storing files on a disk?
A．I-nodes
B．a linked list allocation
C．a continuous allocation
二级建造师入口
D．a linked list with index </P><P>
  (70) Which of the followings is NOT a condition for deadlock?
A．Starvation
B．Circular Wait
C．No Preemption
D．Mutual Exclusion </P><P>
  (71) Assume that an operating system uses a round-robin scheduler. The process’s quantum is 20 msec,and the context switch is 5 msec. What percentage of the CPU’s time is spent on administrative overhead? (2 grades)
A．5％
B．15％
C．20％
D．25％ </P><P>
  (72) What state is a process in when it can’t run because it needs a resource to become
available? (2 grades)
A．Ready
B．Interrupt
C．Blocked
D．Running </P><P>
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  (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)
A．1,9,11,12,16,34,36
B．11,1,36,16,34,9,12
C．11,12,9,16,1,34,36
D．11,12,16,34,36,9,1 </P><P>