What are the characteristics of friend functions in C++?

Characteristics of C++ friend functions include:

1. Friend functions have unrestricted access to a class’s private and protected members, allowing them to access and manipulate a class’s private data from outside the class.
2. A friend function is not a member function of a class, it can exist independently from the class. It can be defined within or outside of the class.
3. The declaration of a friend function needs to be inside the class, but the definition can be inside or outside the class. The declaration of a friend function uses the keyword “friend”.
4. Friend functions can be declared as friends by multiple classes and can also be member functions of another class.
5. Friend functions can be called directly using the function name without the need to go through an object. In other words, friend functions do not need to access the class members through objects.
6. The parameters of a friend function can be objects of a class or other types of data.

It’s important to note that while friend functions provide access to a class, they can also undermine the class’s encapsulation and potentially decrease code maintainability. Therefore, when using friend functions, it is important to carefully consider and avoid overuse.