What is the difference between static and non-static classes in C++?

There are some differences in the definition and usage of static and non-static classes in C++.

1. Static class: In a static class, both member functions and member variables must be static. A static class cannot be instantiated, and the this pointer cannot be used. Member functions and member variables of a static class can be accessed directly by the class name, without needing to create an instance of the class. Static classes are typically used to implement a group of related static functions and variables, without requiring instantiation of class objects.
2. Non-static class: In a non-static class, member functions and member variables can be either static or non-static. Non-static classes can be instantiated, and member functions and member variables can be accessed through instantiated objects. Member functions of non-static classes can use the “this” pointer to access the member variables of the current object. Non-static classes are typically used to represent specific objects and entities, and need to be instantiated to be used.

In general, the difference between static classes and non-static classes lies in the fact that static classes are mainly used to implement a set of related static functions and variables without the need for instantiation; whereas non-static classes are used to represent specific objects and entities that require instantiation to be used.