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Output of C++ Program | Set 10
  • Difficulty Level : Easy
  • Last Updated : 05 May, 2021

Predict the output of following C++ programs.
Question 1
 

C




#include<iostream>
#include<string.h>
using namespace std;
 
class String
{
    char *p;
    int len;
public:
    String(const char *a);
};
 
String::String(const char *a)
{
    int length = strlen(a);
    p = new char[length +1];
    strcpy(p, a);
    cout << "Constructor Called " << endl;
}
 
int main()
{
    String s1("Geeks");
    const char *name = "forGeeks";
    s1 = name;
    return 0;
}

Output: 
 

Constructor called
Constructor called

The first line of output is printed by statement “String s1(“Geeks”);” and the second line is printed by statement “s1 = name;”. The reason for the second call is, a single parameter constructor also works as a conversion operator (See this and this for details). 
Question 2 
 

CPP




#include<iostream>
 
using namespace std;
 
class A
{
    public:
    virtual void fun() {cout << "A" << endl ;}
};
class B: public A
{
    public:
    virtual void fun() {cout << "B" << endl;}
};
class C: public B
{
    public:
    virtual void fun() {cout << "C" << endl;}
};
 
int main()
{
    A *a = new C;
    A *b = new B;
    a->fun();
    b->fun();
    return 0;
}

Output: 
 

C
B

A base class pointer can point to objects of children classes. A base class pointer can also point to objects of grandchildren classes. Therefore, the line “A *a = new C;” is valid. The line “a->fun();” prints “C” because the object pointed is of class C and fun() is declared virtual in both A and B (See this for details). The second line of output is printed by statement “b->fun();”.
Please write comments if you find any of the answers/explanations incorrect, or want to share more information about the topics discussed above.
 

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