What is the difference between a class and a struct in C++?

In C++, both classes and structs are used to define user-defined data types, but they have some key differences in terms of their default member accessibility and their intended use.

The main difference between a class and a struct in C++ is the default member accessibility. In a class, members are private by default, whereas in a struct, members are public by default. However, this can be overridden using access specifiers such as public, protected, and private.

Here’s an example of a class in C++:

    class Person {
        public:
        Person(std::string name, int age) {
            this->name = name;
            this->age = age;
        }
        
        void sayHello() {
            std::cout << "Hello, my name is " << name << " and I'm " << age << " years old." << std::endl;
        }
        
        private:
        std::string name;
        int age;
    };

And here’s an equivalent example using a struct:

    struct Person {
        public:
        Person(std::string name, int age) {
            this->name = name;
            this->age = age;
        }
        
        void sayHello() {
            std::cout << "Hello, my name is " << name << " and I'm " << age << " years old." << std::endl;
        }
        
        private:
        std::string name;
        int age;
    };

As you can see, the main difference between the two is the keyword used to define the data type. In practice, however, the choice between using a class or a struct often comes down to the intended use of the data type.

Classes are often used to define complex, object-oriented data types, whereas structs are often used to define simpler data types that are primarily used to group data together. For example, you might use a struct to define a point in 3D space, with x, y, and z coordinates, whereas you might use a class to define a more complex object such as a game character with properties such as health, speed, and position, and methods such as move and attack.

In summary, while classes and structs in C++ are similar in many ways, the main difference between them is their default member accessibility and their intended use. Classes are often used to define more complex object-oriented data types, whereas structs are often used to define simpler data types for grouping data together.