C语言第四章习题答案

1.下列程序中横线处正确的语句应该是（ ） #include using namespace std; class Base {

public; void fun( )

{cout< < “Base : : fun” < < endl;} };

class Derived : public Base {

public: void fun( ) {

_________//显示调用基类的函数fun( ) cout < < “Derived : : fun” < < endl; }

}; A fun( ).

B Base.fun( ) C Base : : fun( ) D Base - >fun( )

2下面程序的执行结果是（ #include class A {

public:

void disp()

{ cout<<\};

class B:public A {

public: void disp()

{cout<<\};

void main() {

B b; b.disp(); }

输出为：class B

1

）

3下面程序的执行结果是（ ） #include class A {public:

A(int I,int j) {a=I;b=j;}

void move(int x,int y) {a+=x;b+=y;} void show()

{cout<<\ private: int a,b; };

class B:private A { public:

B(int I,int j,int k,int l):A(I,j) {x=k;y=l;} void show()

{cout<

void main() { A e(2,3); e.show(); B d(4,5,6,7); d.fun(); d.show(); d.f1(); d.show(); }

输出为：(2,3)

6,7 (6,9)

4下面程序的输出结果为 #include class base {

2

public:

base(int x,int y) {a=x;b=y;} void show()

{cout<<\ private: int a,b; };

class derived:public base {

public:

derived(int x,int y,int z):base(x,y),c(z) {}

void show()

{cout<<\ private: int c; };

int main() {

base b(10,10),*pb; derived d(20,30,40); pb=&b; pb->show(); pb=&d; pb->show(); return 0; }

输出结果为 base:10;10 base:20;305

5、下面程序的输出结果为 #include class AA {

protected: int k; public:

AA(int n=4):k(n) {}

~AA()

{cout<<\

3

virtual void f() const=0; };

inline void AA::f() const {}

class BB:public AA {

public: ~BB()

{cout<<\ void f() const {cout<

int main() {

AA &p=*new BB; p.f();

delete &p; return 0;

}程式的执行结果2AA

6 分析以下程式的执行结果： #include class base { int n; public:

base(){}; base (int a) {

cout << \ n=a;

cout << \ }

~base() { cout << \};

class subs : public base {

int m; public:

subs(int a, int b) : base(a) {

cout << \

4

m=b;

cout << \ }

subs() { cout << \ };

void main () {

subs s(1,2); }

解： 这里base 是基类，subs为派生类，subs类的构造函数中含有调用基本类的构造函数。 所以输出为：

constructing base class n=1

constructing sub class n=2

destructing base class destructing sub class

7 分析以下程式的执行结果: #include class A {

int a; public:

A(int i) { a=i;cout << \ void print() { cout << \

~A() { cout << \ };

class B1:public A {

int b1; public:

B1(int i,int j):A(i)

{ b1=j;cout << \ void print()

{ A::print ();cout << \

~B1(){ cout << \ };

class B2:public A {

int b2; public:

5