Difference between Public and Private in C++ with Example
Last Updated :
15 Oct, 2019
Public
All the class members declared under public will be available to everyone. The data members and member functions declared public can be accessed by other classes too. The public members of a class can be accessed from anywhere in the program using the direct member access operator (.) with the object of that class.
Example:
#include <iostream>
using namespace std;
class Circle {
public :
double radius;
double compute_area()
{
return 3.14 * radius * radius;
}
};
int main()
{
Circle obj;
obj.radius = 5.5;
cout << "Radius is: " << obj.radius << "\n" ;
cout << "Area is: " << obj.compute_area();
return 0;
}
|
Output:
Radius is: 5.5
Area is: 94.985
In the above program, the data member radius is public so we are allowed to access it outside the class.
Private
The class members declared as private can be accessed only by the functions inside the class. They are not allowed to be accessed directly by any object or function outside the class. Only the member functions or the friend functions are allowed to access the private data members of a class.
Example:
#include <iostream>
using namespace std;
class Circle {
private :
double radius;
public :
void compute_area( double r)
{
radius = r;
double area = 3.14 * radius * radius;
cout << "Radius is: " << radius << endl;
cout << "Area is: " << area;
}
};
int main()
{
Circle obj;
obj.compute_area(1.5);
return 0;
}
|
Output:
Radius is: 1.5
Area is: 7.065
Difference between Public and Private
Public |
Private |
|
|
All the class members declared under public will be available to everyone. |
The class members declared as private can be accessed only by the functions inside the class. |
The data members and member functions declared public can be accessed by other classes too. |
Only the member functions or the friend functions are allowed to access the private data members of a class. |
The public members of a class can be accessed from anywhere in the program using the direct member access operator (.) with the object of that class. |
They are not allowed to be accessed directly by any object or function outside the class. |
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