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％
2019年全国计算机等级考试四级模拟试题及答案7
