The constructors in C++ can be classified as
- Default Constructors
- Parameterized Constructors
- Copy Constructors
1. Default Constructors
A constructor that does not take
any parameter (argument) is called a default constructor. It simply allocates
storage for the data members.
Ex.
//Demonstration on Default
constructor
#include<iostream.h>
#include<conio.h>
class sample
{
private:
int n;
public:
sample()
{ n=100; }
void show()
{
cout<<"\n N=
"<<n;
}
};
void main()
{
sample s;
s.show();
}
2. Parameterized Constructors:-
A constructor that is defined with
parameters is called a parameterized constructor. It is used to initialize the
data members of a class.
For a parameterized constructor,
the data will be sending through that class object declaration only, because
constructors are executed by the object declaration.
Ex. //Demonstration on
parameterized constructor
#include<iostream.h>
#include<conio.h> class
sample
{
private: int n; public:
sample(int k)
{
n=k;
}
void show()
{
cout<<"\n N=
"<<n;
}
};
void main()
{
clrscr();
sample s1(50);
s1.show();
getch();
}
3. Copy Constructors
It is used to copy the data values
of one object into the members of another object. This constructor takes an
object of the class as an argument.
It takes only one argument, also
known as one argument constructor.
It creates a new object from an
existing one by initialization. A copy constructor takes a reference to an
object of the same class as an argument.
Ex.
//Demonstration on copy constructor
#include<iostream.h>
#include<conio.h>
class sample
{
private:
int n;
public:
sample(int k)
{
n=k;
}
sample(sample &s)
{
n=s.n;
}
void show()
{
cout<<"\n N=
"<<n;
}
};
void main()
{
clrscr();
sample s1(50);
s1.show();
sample s2(s1);
s2.show();
getch();
}
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