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Set values of data members using default, parameterized and copy constructor in C++

Here, we are going to learn how to set values to the data members in a class using default, parameterized and copy constructor in C++?
Submitted by IncludeHelp, on September 27, 2018 [Last updated : March 02, 2023]

How to set values of data members using default, parameterized and copy constructor in C++?

Create a class and set values to the private data members using a default, parameterized and copy constructor in C++.

This is an example of C++ constructors, here we have a class named person and private data members name and age. In this example, we will set values to name and age through the default, parameterized and copy constructors.

Here, we will create three objects p1, p2 and p3. p1 will be initialized with a default constructor, p2 will be initialized with a parameterized constructor and p3 will be initialized with the copy constructor.

C++ program to set values of data members using default, parameterized and copy constructor

#include <iostream>
#include <string.h>
using namespace std;

class person {
private:
    char name[30];
    int age;

public:
    //default constructor
    person()
    {
        strcpy(name, "None");
        age = 0;
    }
    //parameterized constructor
    person(char n[], int a)
    {
        strcpy(name, n);
        age = a;
    }
    //copy constructor
    person(person& p)
    {
        strcpy(name, p.name);
        age = p.age;
    }
    //function to display person details
    void print(void)
    {
        cout << name << " is " << age << " years old." << endl;
    }
};

//Main function
int main()
{
    //creating objects
    //default constructor will be called
    person p1;
    //parameterized constructor will be called
    person p2("Amit Shukla", 21);
    //copy constructor will be called
    person p3(p2);

    //printing
    cout << "object p1..." << endl;
    p1.print();
    cout << "object p2..." << endl;
    p2.print();
    cout << "object p3..." << endl;
    p3.print();

    return 0;
}

Output

object p1...
None is 0 years old.
object p2...
Amit Shukla is 21 years old.
object p3...
Amit Shukla is 21 years old.