This guide shows you how to use C++ classes and objects. You will learn what they are. You will also see how they work with clear examples.<\/p>\n\n\n\n
A C++ class is a user-defined data type that serves as a template for creating objects. It defines the structure and behavior of the objects by specifying the data (variables) and functions (methods) that operate on that data.<\/p>\n\n\n\n
You use classes to describe properties and actions. For example, a \"Car\" class might have properties like \"color\" and \"speed.\" It might also have actions like \"start\" and \"stop.\"<\/p>\n\n\n\n
Here's why classes matter:<\/p>\n\n\n\n
You define a class using the Here is a simple example of a In this example, A C++ object is a real instance of a class. If a class is a blueprint, an object is the actual house built from that blueprint. You create many objects from one class blueprint. Each object has its own set of data.<\/p>\n\n\n\n For example, from the Each of these is a You create an object by declaring a variable of the class type.<\/p>\n\n\n\n Here\u2019s how you create In You access data members and member functions of an object using the dot ( Here's how you work with When you run this code, you see output that shows each car's details and actions.<\/p>\n\n\n Classes use access specifiers<\/b> to control how you access their members.<\/p>\n\n\n\n Here's an example with private members:<\/p>\n\n\nclass<\/code> keyword. You give it a name. Then you put its members inside curly braces {}<\/code>.<\/p>\n\n\n\nCar<\/code> class:<\/p>\n\n\n\nclass Car {\npublic:\n \/\/ Properties (data members)\n std::string color;\n int speed;\n\n \/\/ Actions (member functions)\n void start() {\n \/\/ Code to start the car\n }\n\n void stop() {\n \/\/ Code to stop the car\n }\n};\n<\/pre><\/div>\n\n\nCar<\/code> is the name of the class. color<\/code> and speed<\/code> are data members which store information. start()<\/code> and stop()<\/code> are member functions which perform actions. public:<\/code> means you can access these members from outside the class.<\/p>\n\n\n\nWhat is a C++ Object?<\/h2>\n\n\n\n
Car<\/code> blueprint, you can create:<\/p>\n\n\n\n\n
Car<\/code> object. They both come from the Car<\/code> class.<\/p>\n\n\n\nCreating an Object<\/h3>\n\n\n\n
Car<\/code> objects:<\/p>\n\n\n\n#include <iostream> \/\/ Needed for output\n#include <string> \/\/ Needed for string type\n\nclass Car {\npublic:\n std::string color;\n int speed;\n\n void start() {\n std::cout << "The " << color << " car is starting." << std::endl;\n }\n\n void stop() {\n std::cout << "The " << color << " car is stopping." << std::endl;\n }\n};\n\nint main() {\n Car car1; \/\/ Create an object named car1\n Car car2; \/\/ Create another object named car2\n\n return 0;\n}\n<\/pre><\/div>\n\n\nmain()<\/code>, car1<\/code> and car2<\/code> are objects of the Car<\/code> class. They are separate cars.<\/p>\n\n\n\nAccessing Class Members<\/h3>\n\n\n\n
.<\/code>) operator.<\/p>\n\n\n\ncar1<\/code> and car2<\/code>:<\/p>\n\n\n\n#include <iostream>\n#include <string>\n\nclass Car {\npublic:\n std::string color;\n int speed;\n\n void start() {\n std::cout << "The " << color << " car is starting." << std::endl;\n }\n\n void stop() {\n std::cout << "The " << color << " car is stopping." << std::endl;\n }\n};\n\nint main() {\n Car car1; \/\/ Create car1 object\n car1.color = "Red"; \/\/ Set car1's color\n car1.speed = 100; \/\/ Set car1's speed\n\n Car car2; \/\/ Create car2 object\n car2.color = "Blue"; \/\/ Set car2's color\n car2.speed = 120; \/\/ Set car2's speed\n\n std::cout << "Car 1: Color = " << car1.color << ", Speed = " << car1.speed << std::endl;\n car1.start(); \/\/ Call start() function for car1\n\n std::cout << "Car 2: Color = " << car2.color << ", Speed = " << car2.speed << std::endl;\n car2.stop(); \/\/ Call stop() function for car2\n\n return 0;\n}\n<\/pre><\/div>\n\n\n\nCar 1: Color = Red, Speed = 100\nThe Red car is starting.\nCar 2: Color = Blue, Speed = 120\nThe Blue car is stopping.\n<\/pre><\/div>\n\n\n
Public and Private Access Specifiers<\/h3>\n\n\n\n
\n
public:<\/code><\/b> You can access public members from anywhere in the program. You saw this in the Car<\/code> class example.<\/li>\n\n\n\nprivate:<\/code><\/b> You can only access private members from inside the class itself. You cannot access them directly from outside the class. This protects data.<\/li>\n<\/ul>\n\n\n\n\n#include <iostream>\n#include <string>\n\nclass Dog {\nprivate:\n std::string name; \/\/ Private data member\n int age; \/\/ Private data member\n\npublic:\n \/\/ Public functions to set and get private data\n void setName(std::string n) {\n name = n;\n }\n\n std::string getName() {\n return name;\n }\n\n void setAge(int a) {\n if (a > 0) { \/\/ Add a check for valid age\n age = a;\n } else {\n std::cout << "Age cannot be zero or negative." << std::endl;\n }\n }\n\n int getAge() {\n return age;\n }\n\n void bark() {\n std::cout << name << " barks loudly!" << std::endl;\n }\n};\n\nint main() {\n Dog myDog;\n\n \/\/ myDog.name = "Buddy"; \/\/ This would cause an error! 'name' is private.\n\n myDog.setName("Buddy"); \/\/ Use public function to set name\n myDog.setAge(3); \/\/ Use public function to set age\n\n std::cout << "My dog's name is " << myDog.getName() << std::endl;\n std::cout << "My dog's age is " << myDog.getAge() << std::endl;\n myDog.bark();\n\n myDog.setAge(-1); \/\/ This will show an error message from setAge\n\n return 0;\n}\n<\/pre><\/div>\n\n\n