What is a Class?

A class is a user-defined type.

It describes what kind of data an object will store and what actions the object can perform.

Simple definition:

A class is a blueprint for creating objects.

Example Idea

Think about a Student.

A student object may have:

• name
• id
• marks

And it may perform actions:

• display details
• update marks
• check pass/fail

The class describes this structure.

Basic Class Example

#include <iostream>
#include <string>

class Student {
private:
    std::string name;
    int marks;

public:
    void setDetails(const std::string& studentName, int studentMarks) {
        name = studentName;
        marks = studentMarks;
    }

    void display() const {
        std::cout << name << " scored " << marks << '\n';
    }
};

int main() {
    Student student;
    student.setDetails("Mina", 85);
    student.display();
}

What the Class Contains

Does a Class Definition Use Object Memory?

The class definition itself is a type description. It does not create a real student object.

Memory for non-static data members is needed when you create an object.

Student s1; // object created
Student s2; // another object created

Connection to OOP

A class is where OOP starts in C++.

It lets you group:

• state: data members
• behavior: member functions

Viva Answer

A class is a user-defined type or blueprint that defines the data members and member functions of its objects. The class itself describes the structure; objects are the actual instances created from it.

Quick Check

• What is a class?
• What are data members?
• What are member functions?
• Does writing a class definition create an object?