Classes and objects (brief introduction)

At this point in the class, all we have seen are variables and types. We’ll look at “classes” very briefly here, so we can become familiar with the concept before we truly exploit it.

A class defines a new type. Like int is a type, we can create our own type, maybe called Person. (We typically capitalize types that we create with classes.) Class types are always built out of other types; you can think of a class as a composite of other types.

For example, here we define the Person class:

// this goes above "main()"

class Person
{
public:
    string name;
    int age;       // in years
    double height; // in cm
    double weight; // in kg
};

Once we have defined the class, we can create objects of that type. In this case, the class is Person (a general idea or classification) and each object will represent some particular person:

int main()
{
    Person vignesh;
    vignesh.name = "Vignesh S.";
    vignesh.age = 25;
    vignesh.height = 177;
    vignesh.weight = 68;
    
    cout << vignesh.name << " weighs " << vignesh.weight << " kg." << endl;
    
    return 0;
}

Classes will appear again in the function lecture notes where we’ll add functions inside the classes.