y=x*x

End If

End If

输出y.

该算法语句的功能是(　　)

A.输入一个数x,并比较x与0的大小

B.求函数y={■(x+4"," x<0"," @x^2 "," x=0"," @0"," x>0)┤的函数值

C.求函数y={■(x+4"," x<0"," @0"," x=0"," @x^2 "," x>0)┤的函数值

D.以上都不对

解析:此算法涉及复合If语句,分x>0,x=0,x<0三种情况讨论,且相应的y的表达式也不同,故它的功能是求一个分段函数的函数值,易知此函数为y={■(x+4"," x<0"," @0"," x=0"," @x^2 "," x>0"." )┤

答案:C

5.为了在运行下面的算法语句之后输出y=9,键盘输入应该是(　　)

输入x;

If x<0 Then

　y=(x+1)*(x+1)

Else

　y=(x-1)*(x-1)

End If

输出y.

A.x=-4

B.x=-2

C.x=4或x=-4

D.x=2或x=-2

解析:当x<0时,由(x+1)·(x+1)=9,得x=-4;

当x≥0时,由(x-1)·(x-1)=9,得x=4,故x=4或x=-4.

答案:C

6.给出下列算法语句:

输入x1,x2;

If　x1=x2　Then

y=x1-x2

Else

y=x1+x2

End If

输出y.

如果输入x1=2,x2=3,那么输出的y是(　　)