What characterizes a class variable in OOP?

A class variable is defined as a variable that is shared among all instances of a class. This means that regardless of how many objects (instances) of that class are created, they all reference the same single instance of the class variable. This shared nature allows for a uniform property or state that can be accessed and modified by all instances.

For example, if you have a class representing a bank account, a class variable could be used to track the interest rate for all accounts. If the interest rate changes, it affects all instances of that class immediately, as they all share the same variable.

In contrast, instance variables are unique to each instance, meaning changes to one instance's variable do not impact others. A variable that cannot be modified would refer to a constant, which doesn't describe a class variable. Lastly, a variable that is local to one method only is typically known as a local variable, and it cannot be accessed outside of that method's scope, distinguishing it from class variables that are accessible throughout the class.