多选题class BaseClass{  private float x= 1.0f；  protected void setVar （float f） {x = f；}  } class SubClass extends BaseClass   {  private float x = 2.0f；  //insert code here 16. }   Which two are valid examples of method overriding？（）AVoid setVar（float f） {x

下列程序的执行结果是______。

include＜iostream.h＞

class Student

{

public:

Student(int xx){x=xx;}

virtual float calcTuition( );

protected:

int x;

};

float Studertt::calcTuition( )

{

return float(x*x);

}

class GraduateStudent:public Student

{

public:

GraduateStudent(int xx):Student(xx){}

float calcTuition( );

};

float Graduatestudent::calcTuition( )

{

return float(x*2);

}

void main( )

{

Student s(20);

GraduateStudent gs(30);

cout＜＜s.calcTuition( )＜＜" "＜＜gs.calcTuition( )＜＜endl;

//计算学生s和研究生gs的学费

}

12 一个给定的数值由左边开始升位到右边第 N 位，如

0010<<1 == 0100

或者

0001 0011<<4 == 0011 0000

请用 C 或者 C++或者其他 X86 上能运行的程序实现。

-----------------------------------------------------------------------------

-----------------------------------

附加题（只有在完成以上题目后，才获准回答）

In C++, what does "explicit" mean? what does "protected" mean?

explicit

C++ Specific

This keyword is a declaration specifier that can only be applied to

in-class constructor declarations. Constructors declared explicit will not

be considered for implicit conversions. For example:

class X {

public:

explicit X(int); //legal

explicit X(double) { //legal // ... }

};

explicit X::X(int) {} //illegal

An explicit constructor cannot take part in implicit conversions. It can

only be used to explicitly construct an object. For example, with the class

declared above:

void f(X) {}

void g(int I)

{

f(i); // will cause error

}

void h()

{

X x1(1); // legal

}

The function call f(i) fails because there is no available implicit

conversion from int to X.

Note It is meaningless to apply explicit to constructors with multiple

arguments, since such constructors cannot take part in implicit conversions.

END C++ Specific

protected

C++ Specific —>

protected: [member-list]

protected base-class

When preceding a list of class members, the protected keyword specifies

that those members are accessible only from member functions and friends of

the class and its derived classes. This applies to all members declared up

to the next access specifier or the end of the class.

When preceding the name of a base class, the protected keyword specifies

that the public and protected members of the base class are protected

members of the derived class.

Default access of members in a class is private. Default access of members

in a structure or union is public.

Default access of a base class is private for classes and public for

structures. Unions cannot have base classes.

For related information, see public, private, friend, and Table of Member

Access Privileges.

END C++ Specific

Example

// Example of the protected keyword

class BaseClass {

protected: int protectFunc();

};

class DerivedClass : public BaseClass

{ public:

int useProtect() { protectFunc(); } // protectFunc accessible from

derived class

};

void main()

{

BaseClass aBase;

DerivedClass aDerived;

aBase.protectFunc(); // Error: protectFunc not accessible

aDerived.protectFunc(); // Error: protectFunc not accessible in derived

class } How do you code an infinite loop in C?

下面程序中错误之处是 ______。

include＜iostream.h＞

class A{

private：

int xl;

protected:

int x2;

public:

int x3;

};

class B: public A{

private:

int b1;

protected:

int b2;

public:

int b3;

void disp(){cout＜＜x1＜＜b2＜＜end1;} //A

void set(int i){x3=i;} //B

};

void main()

B bb;

bb. a3=10 //C

bb. b3=10 //D

}

若有以下程序： #include ＜iostream＞ using namespace std; class Base { private: int x; protected: int y; public: int z; void setx(int i) { x=i; int getx () { return x; } }

A．1,2,3,4

B．产生语法错误

C．4,3,2,1

D．2,3,4,5

有以下程序： #include ＜iostream＞ using namespace std; class A { private: int x,y; public: void set (int i,int j) { x=i; y=j; } int get_y() { return y; } }; class box { private: int length,width; A label; public: void set(int 1,int w, int s,int p) { length=1; width=w; label.set(s,p); } int get_area() { return length*width; } }; int main() { box small; small.set(2,4,1,35); cout＜＜small.get_area()＜＜end1; return 0; } 运行后的输出结果是( )。

A．8

B．4

C．35

D．70

若有以下程序： #include ＜iostream＞ using namespace std; class A { private: int x; protected: int y; public: int z; void setx(int i) { x=i; } int getx () { return x; }; class B : protected A { public: void setvalue(int a, int b, int c) { setx (a); y=b; z=c; } void display() { cout＜＜getx ( ) ＜＜", "＜＜y＜＜", "＜＜z＜＜", "＜＜end1; } }; int main () { B obj; obj.setvalue(5, 6, 7); obj.display ( ); return 0; } 程序运行后的输出结果是( )。

A．产生语法错误

B．7,6,5

C．5,6,7

D．7,5,6

请找出下列程序中错误之处 ______。

#include＜iostream.h＞

class A{

private：

int x1；

protected：

int x2；

public：

int x3；

};

class B：public A{

private：

int y1；

protected：

int y2；

public：

int y3；

void disp(){cout＜＜x1＜＜y1＜＜end1：} //A

void set(int i) {x2=i；} //B

}；

void main() {

B bb；

bb.x3=10； //C

bb.y3=10； //D

}

A．A

B．B

C．C

D．D