Understanding Classes
In C++, a class is a blueprint for creating objects. It defines the structure and behavior of those objects. A class consists of data members (attributes) and member functions (methods).
Specifying a Class
To specify a class, you use the class keyword followed by the class name. The class body is enclosed in curly braces ({}).
C++
class MyClass {
// Data members
// Member functions
};
Defining Data Members
Data members are variables that store the data associated with an object. They can be of any valid C++ data type (e.g., int, float, char, string).
C++
class Person {
public:
string name;
int age;
};
Defining Member Functions
Member functions are functions that operate on the data members of a class. They can be used to access, modify, or process the data associated with an object.
C++
class Person {
public:
string name;
int age;
void displayInfo() {
cout << "Name: " << name << endl;
cout << "Age: " << age << endl;
}
};
Creating Objects
To create an object from a class, you use the new operator or simply declare a variable of that class type.
C++
Person person1;
Person* person2 = new Person();
Accessing Data Members and Calling Member Functions
You can access the data members and call the member functions of an object using the dot operator (.).
C++
person1.name = "Alice";
person1.age = 25;
person1.displayInfo();
Example Program
C++
#include <iostream>
#include <string>
using namespace std;
class Circle {
public:
double radius;
double calculateArea() {
return 3.14159 * radius * radius;
}
};
int main() {
Circle myCircle;
myCircle.radius = 5.0;
cout << "Area of the circle: " << myCircle.calculateArea() << endl;
return 0;
}
Output:
Area of the circle: 78.5398
In this example, the Circle class has a data member radius and a member function calculateArea(). The main function creates a Circle object and sets its radius. Then, it calls the calculateArea() function to calculate and print the area of the circle.
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