一、单项选择题（本大题共20小题，每小题1分，共20分）

在每小题列出的四个备选项中只有一个是符合题目要求的，请将其代码填写在题后的括号内。错选、多选或未选均无分。

1．下面哪种设备是输入设备？(     )

A.键盘                                                      B．打印机

C．显示器                                                D．投影仪

2．与十进制39等值的二进制数是(     )

A.00100111                                               B.01001001

C.10100111                                               D.01011000

3．设有 int a=3，b=-4;表达式(a<b)? a b：（a-b，b 4，a-=b 4）的值是(     )

A.-1                                                          B．0

C．3                                                        D．7

4．设有int a=3,b=-4，c=5;表达式a=b=c=6 3/5的值是(     )

A.3                                                           B．4

C．6                                                        D．6.6

5．以十进制无符号形式输出整数的格式说明符是(     )

A. %u                                                       B．% x

C．%o                                                     D．%d

6．下列程序段执行后的输出结果为

int i =-1;

if(i<=0)    printf(＂* * * * \n＂);

else printf (＂%%%%＼n＂);  (      )

A. * * * * c                                               B.% % % %

C. % % % % c                                          D.** * *

7．执行下面程序段后的y值是

int y=l, x=5；

if(x<0)y=-1；

if(x>=0)y=0;  (      )

A.-1                                                          B．0

C．1                                                        D．5

8．执行while（表达式）结构循环的条件是(     )

A．当表达式的值为0时                           B．仅当表达式的值为l时

C．当表达式的值为非0时                       D．当表达式的值不为1时

9．下面程序段的输出结果是

a=100;

while (a>120)

a= a l;

printf (＂%d", a);  （      ）

A.100                                                       B．101

C．120                                                     D.121

10.下面程序执行后，i的值是

main()

{   int  a[5]={1,2,3,4,5），i =2;

printf (＂%d＂，a[ i ])；

} (      )

A．1                                                        B．2

C．3                                                        D．4