What is Constructor in C++ ?

• In C++ constructor is a special type of member function of a class which initializes objects of a class.
• Constructor is automatically called when object is created in C++.
• It does not have any return type because it is special member function of the class.
• In public section of class and it has same name as the class itself.
• Copy and parameterized constructors have input arguments, by default constructors don’t have input argument however.
• C++ compiler generates a default constructor for object, if we do not specify a constructor.
• In constructor there are three types, they are default constructor, parameterized constructor, copy constructor.

Default Constructor

• It is the constructor which has no parameters and doesn’t take any argument.

Sample Code

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Output

Parameterized Constructor

• It is possible to pass arguments to constructors and these arguments help initialize an object when it is created typically.

Sample Code

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 Output

Copy Constructor

• It is a member function which initializes an object using another object of the same class.

Sample Code

[pastacode lang=”cpp” manual=”using%20namespace%20std%3B%0A%0Aclass%20point%0A%0A%7B%0A%0Aprivate%3A%0A%0A%C2%A0%C2%A0double%20x%2C%20y%3B%0A%0A%0A%0A%0Apublic%3A%0A%0A%C2%A0%C2%A0%C2%A0%0A%0A%C2%A0%C2%A0%2F%2F%20Non-default%20Constructor%20%26%0A%0A%C2%A0%C2%A0%2F%2F%20default%20Constructor%0A%0A%C2%A0%C2%A0point%20(double%20px%2C%20double%20py)%0A%0A%C2%A0%C2%A0%7B%0A%0A%C2%A0%C2%A0%C2%A0%C2%A0x%20%3D%20px%2C%20y%20%3D%20py%3B%0A%0A%C2%A0%C2%A0%7D%0A%0A%7D%3B%0A%0A%0A%0A%0Aint%20main(void)%0A%0A%7B%0A%0A%0A%0A%0A%C2%A0%C2%A0%2F%2F%20Define%20an%20array%20of%20size%0A%0A%C2%A0%C2%A0%2F%2F%2010%20%26%20of%20type%20point%0A%0A%C2%A0%C2%A0%2F%2F%20This%20line%20will%20cause%20error%0A%0A%C2%A0%C2%A0point%20a%5B10%5D%3B%0A%0A%0A%0A%0A%C2%A0%C2%A0%2F%2F%20Remove%20above%20line%20and%20program%0A%0A%C2%A0%C2%A0%2F%2F%20will%20compile%20without%20error%0A%0A%C2%A0%C2%A0point%20b%20%3D%20point(5%2C%206)%3B%0A%0A%7D” message=”” highlight=”” provider=”manual”/]

Output