2019年全国计算机等级考试四级模拟试题及答案7

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 period is

，the shortest

A

Instruction ． period

BMachine period

C

．

Beat period CPU period D

．

． (62) Which set is empty?

A． X2-xx is a real number and x2=9 B) 1=0 }

C){XX is a real number and X2+1=0 and X=2X+1 }

xx is a real number

and

} D) {XX is a real number

(63) What is the relation represented in the

eXhibit shown below?

R={(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)} ．

(64) What is the contrapositive of the following

A

implication? “If it is raining ，then I get wet. ”

A．If I get wet raining.

，then it is

B． If I am wet ，then if is

raining.

If it is not raining, I do not C．

get wet.

If I do not get wet ， then it is not D．

raining.

(65) Which property does R posses? (2 grades)

Let A={1,2,3,4} and let R ={,,,} A． Symmetry B． Reflexivit

y C． Asymmetry Antisymmetry D．

(66) When walking a tree, which traversal method

yields a prefix, or Polish,form?

lnordeA． r

Preorder B． C． Postorder D． 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 not be unique.

C． Finding critical path is an operation on directed

graph.

Finding critical path is an operation on undirected D．

graph.

(68) Which traversal method for a binary tree does the following Pascal code illustrate? (2 grades) procedure traverse(p ：pointer); begin if 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 D．a linked list with index

(70) Which of the followings is NOT a condition for deadlock? A．S tarvation B．C ircular Wait C．N o Preemption D．M utual Exclusion

(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 on administrative overhead? (2 grades)

's time is spent

A．5 ％ B．1 5％