An interface describes the behavior or capabilities of a C++ class without committing to a particular implementation of that class.
The C++ interfaces are implemented using abstract classes and these abstract classes should not be confused with data abstraction which is a concept of keeping implementation details separate from associated data.
A class is made abstract by declaring at least one of its functions as pure virtual function. A pure virtual function is specified by placing "= 0" in its declaration as follows:
#include <iostream.h>
class Shape
{
public:
// pure virtual function providing interface framework.
virtual int getArea() = 0;
void setWidth(int w)
{
width = w;
}
void setHeight(int h)
{
height = h;
}
protected:
int width;
int height;
};
class Rectangle: public Shape
{
public:
int getArea()
{
return (width * height);
}
};
class Triangle: public Shape
{
public:
int getArea()
{
return (width * height)/2;
}
};
int main(void){
Rectangle Rect;
Triangle Tri;
Rect.setWidth(5);
Rect.setHeight(7);
cout << "Total Rectangle area: " << Rect.getArea() << endl;
Tri.setWidth(5);
Tri.setHeight(7);
cout << "Total Triangle area: " << Tri.getArea() << endl;
return 0;
}
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