STATIC DATA MEMBERS & STATIC MEMBER FUNCTIONS ( METHODS)

 STATIC DATA MEMBERS & STATIC MEMBER FUNCTIONS

Static data members & static member functions (methods):- 

A static data member is a class variable shared by all objects of that class.

 

Key Characteristics

1. Only one copy exists for the entire class (not per object).
2. Shared by all instances of the class.
3. Stored in global/static memory, not inside objects.
4. Must be declared inside the class and defined outside the class.
5. Accessed using:
• Object: obj.x
• Class name: ClassName::x (recommended)

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Use of Static Data Members

·       Maintain common information for all objects.

·       Use as counters (e.g., number of objects created).

·       Use as constants inside class (static const).

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Example (Static Data Member)

 

#include <iostream>

using namespace std;

 

class Student {

    static int count;   // declaration

public:

    Student() {

        count++;       // increase when object created

    }

    static int getCount() {

        return count;

    }

};

 

// definition outside class

int Student::count = 0;

 

int main() {

    Student s1, s2, s3;

    cout << "Total students: " << Student::getCount();

    return 0;

}

 

OUTPUT

Total students: 3

 

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 STATIC MEMBER FUNCTIONS (METHODS)

 A static member function:

• Belongs to the class, not to any object.
• Called without creating an object.
• Access only static data members, not normal members.

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Key Features

No, this pointer is available
Access only static members
Usually used to manipulate static data members
Access using:

• ClassName::function() (preferred)
• or through object

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Example (Static Member Function)

#include <iostream>

using namespace std;

 

class Test {

private:

    static int value;

public:

    static void setValue(int v) {

        value = v;  // allowed

        // x = 5;   // ❌ not allowed (x is non-static)

    }

 

    static void showValue() {

        cout << "Value = " << value << endl;

    }

};

 

int Test::value = 0;

 

int main() {

    Test::setValue(50);

    Test::showValue();

    return 0;

}

 

OUTPUT

Value = 50

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SUMMARY TABLE

Feature	Static Data Member	Static Member Function
Belongs to	Class	Class
copies	One per class	Only one function
Need an object	No	No
Can access	Static + Non-static	Only static
Uses	Counters, Shared values	Utility functions

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