Interesting Fact (Rare Known Concept)
Why do we give semicolons at the end of class?
Many people might say that it’s a basic syntax and we should give a semicolon at the end of the class as its rule defines in cpp. But the main reason why semi-colons are there at the end of the class is compiler checks if the user is trying to create an instance of the class at the end of it.
Yes just like structure and union, we can also create the instance of a class at the end just before the semicolon. As a result, once execution reaches at that line, it creates a class and allocates memory to your instance.
C++
#include <iostream> using namespace std; class Demo{ int a, b; public: Demo() // default constructor { cout << "Default Constructor" << endl; } Demo(int a, int b):a(a),b(b) //parameterised constructor { cout << "parameterized constructor -values" << a << " "<< b << endl; } }instance; int main() { return 0; } |
Default Constructor
We can see that we have created a class instance of Demo with the name “instance”, as a result, the output we can see is Default Constructor is called.
Similarly, we can also call the parameterized constructor just by passing values here
C++
#include <iostream> using namespace std; class Demo{ public: int a, b; Demo() { cout << "Default Constructor" << endl; } Demo(int a, int b):a(a),b(b) { cout << "parameterized Constructor values-" << a << " "<< b << endl; } }instance(100,200); int main() { return 0; } |
parameterized Constructor values-100 200
So by creating an instance just before the semicolon, we can create the Instance of class.
Related Articles:
C++ Classes and Objects
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 brands but all of them will share some common properties like all of them will have 4 wheels, Speed Limit, Mileage range, etc. So here, Car is the class, and wheels, speed limits, and mileage are their properties.
- A Class is a user-defined data type that has data members and member functions.
- Data members are the data variables and member functions are the functions used to manipulate these variables together, these data members and member functions define the properties and behavior of the objects in a Class.
- In the above example of class Car, the data member will be speed limit, mileage, etc, and member functions can be applying brakes, increasing 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.