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Engineering LibreTexts

1.8: Classes and Objects

  • Page ID
    34640
  • Class: A class in C++ is the building block, that leads to Object-Oriented programming. It is a user-defined data type, which holds its own data members and member functions, which can be accessed and used by creating an instance of that class. A C++ class is like a blueprint for an object.
    For Example: Consider the Class of Cars. There may be many cars with different names and brand but all of them will share some common properties like all of them will have 4 wheelsSpeed LimitMileage range etc. So here, Car is the class and wheels, speed limits, mileage are their properties.

    • A Class is a user defined data-type which has data members and member functions.
    • Data members are the data variables and member functions are the functions used to manipulate these variables and together these data members and member functions defines the properties and behavior of the objects in a Class.
    • In the above example of class Car, the data member will be speed limitmileage etc and member functions can be apply brakesincrease speed etc.

    An Object is an instance of a Class. When a class is defined, no memory is allocated but when it is instantiated (i.e. an object is created) memory is allocated.

    A class is defined in C++ using keyword class followed by the name of class. The body of class is defined inside the curly brackets and terminated by a semicolon at the end.

    Classes and objects

    Declaring Objects: When a class is defined, only the specification for the object is defined; no memory or storage is allocated. To use the data and access functions defined in the class, you need to create objects.

    Syntax:

    ClassName ObjectName;

    Accessing data members and member functions: The data members and member functions of class can be accessed using the dot(‘.’) operator with the object. For example if the name of object is obj and you want to access the member function with the name printName() then you will have to write obj.printName() .

    Adapted from:
    "C++ Classes and Objects" by Abhirav Kariya, Geeks for Geeks is licensed under CC BY 4.0