Class

Class is a user-defined blueprint from which objects are created. Basically, a class combines the fields(variables) and methods into a single unit. In C++, classes support advance object oriented programming concepts like inheritance, abstraction etc.

Before entering coding part of Class, we need to be clear with concept called Access Modifiers. Access Modifiers are keywords that define the accessibility of a member, class or datatype in a program. These are mainly used to restrict unwanted data manipulation by external programs or classes. There are 3 access modifiers present in C++, let us discuss each with its description.

Public - Accessible everywhere.
Private - Accessible within the same class.
Protected - Accessible within its child class(we'll learn more about this in Inheritance chapter).


CODE

EG 1 . Creating Rectangle class with fields and variables

#include <iostream>
using namespace std;

//Creating class called Rectangle with its fields and methods.
class Rectangle {
    //In order to access fields and methods outside class, we need to use Public keyword.
  public:
    double length, width, height;
    double Area() {
        return length * width;
    }
    double Perimeter() {
        return 2 * (length+width);
    }
    double Volume() {
        return Area() * height;
    }
};

int main() {

}

CODE EXPLANATION
Creating a class called Rectangle and loading that with some sensible fields and methods. If we compile above program nothing will be printed out since we haven't written anything inside main method. It doesn't matter how many classes we are creating, system will directly go inside main method inside program class and execute whatever code we written inside because still that is our entry point.


EG 2 . Creating Class called car with fields and variables

#include <iostream>
using namespace std;

class Car {
  public :
    string color;
    int weight, numberOfSeats;
    void Drive() {
        cout << "Start Driving" << endl;
    }
    double CarryingLoadCapacity() {
        return (numberOfSeats*65)+30; //65 is the average weight of a person in kgs, 30kgs for extra load for accessories,fuel etc.
    }
};

int main() {

}

CODE EXPLANATION
Creating a class called Car and loading that with some sensible fields and methods. If we compile above program, here also nothing will be printed out since we haven't written anything inside main method. Not only the above mentioned fields and methods we can load classes with n number of sensible fields and methods.


Exercises
1. Create a class called MusicalInstruments with fields and methods.
2. Create a class called Circle with fields and methods.
3. Create a class called Triangle with fields and methods.


(Click Here, For more exercises)