1. What is a Class?
A class is a user-defined data type that contains:
- Variables (data members)
- Functions (member functions)
👉 It acts as a blueprint for creating objects.
Syntax:
class ClassName {
access_specifier:
data_members;
member_functions;
};
2. What is an Object?
An object is an instance of a class.
✔ Class = Blueprint
✔ Object = Real-world entity created from class
3. Simple Example
#include <iostream>
using namespace std;
class Student {
public:
int roll;
string name;
void display() {
cout << "Roll: " << roll << endl;
cout << "Name: " << name << endl;
}
};
int main() {
Student s1; // Object creation
s1.roll = 101;
s1.name = "Rahul";
s1.display();
return 0;
}
4. Access Specifiers
Access specifiers define visibility of class members.
Specifier Meaning
public Accessible everywhere
private Accessible only inside class
protected Accessible in derived classes
5. Private Members Example
class Bank {
private:
int balance;
public:
void setBalance(int b) {
balance = b;
}
void showBalance() {
cout << "Balance: " << balance;
}
};
✔ Data hiding achieved using private members.
6. Defining Member Functions Outside Class
#include <iostream>
using namespace std;
class Rectangle {
public:
int length, width;
int area();
};
int Rectangle::area() {
return length * width;
}
int main() {
Rectangle r;
r.length = 5;
r.width = 4;
cout << "Area: " << r.area();
}
7. Multiple Objects
Student s1, s2;
s1.roll = 1;
s2.roll = 2;
Each object has its own copy of data members.
8. Class with Constructor
A constructor initializes objects automatically.
class Demo {
public:
Demo() {
cout << "Constructor called!";
}
};
int main() {
Demo d1;
}
9. Real-Life Example
class Car {
public:
string brand;
int speed;
void start() {
cout << brand << " is starting...";
}
};
Object:
Car c1;
c1.brand = "Tesla";
c1.start();
10. Key Features of Classes
✔ Encapsulation
✔ Data hiding
✔ Code reusability
✔ Modular programming
📌 Difference: Structure vs Class
Feature Structure Class
Default access public private
OOP features Limited Full support
Use case Simple data Complex OOP programs
Member Functions in C++
Member functions are functions defined inside a class that operate on the data members of that class.
1. Definition
- A member function:
- Belongs to a class
- Can access all data members of the class
- Can be defined inside or outside the class
2. Basic Syntax
class ClassName {
public:
void functionName(); // Declaration
};
3. Member Function Defined Inside Class
#include <iostream>
using namespace std;
class Student {
public:
int roll;
string name;
void display() {
cout << "Roll: " << roll << endl;
cout << "Name: " << name << endl;
}
};
int main() {
Student s1;
s1.roll = 101;
s1.name = "Rahul";
s1.display(); // Calling member function
}
✔ Automatically inline when defined inside class.
4. Member Function Defined Outside Class
Step 1: Declaration in class
Step 2: Definition using scope resolution operator ::
#include <iostream>
using namespace std;
class Rectangle {
public:
int length, width;
int area();
};
int Rectangle::area() {
return length * width;
}
int main() {
Rectangle r;
r.length = 5;
r.width = 4;
cout << "Area: " << r.area();
}
👉 ClassName::functionName
5. Accessing Data Members
Member functions can directly access:
- Public members
- Private members
- Protected members
Example:
class Bank {
private:
int balance;
public:
void setBalance(int b) {
balance = b; // Access private member
}
};
6. Types of Member Functions
1.Inline Member Function
Defined inside class → automatically inline.
class Test {
public:
void show() {
cout << "Inline function";
}
};
2. Non-Inline Member Function
Defined outside class.
void Test::show() {
cout << "Non-inline function";
}
3. Const Member Function
Does not modify object data.
class Demo {
public:
int x;
void show() const {
cout << x;
}
};
4. Static Member Function
Belongs to class, not objects.
class Counter {
public:
static int count;
static void showCount() {
cout << count;
}
};
✔ Can access only static members.
0 comments
Post a Comment