where is a variable that has class or global scope declared
Global variable In some languages, all variables are global, or global by default, while in most modern languages variables have limited scope, generally lexical scope, though global variables are often available by declaring a variable at the top level of the program. In other languages, however, global variables do not exist; these are generally modular programming languages that enforce a module structure, or class-based object-oriented programming languages that enforce a class structure.
Inheritance (object-oriented programming) In object-oriented programming, inheritance is when an object or class is based on another object (prototypal inheritance) or class (class-based inheritance), using the same implementation. Inheritance in most class-based object oriented languages is a mechanism in which one object acquires all the properties and behaviors of parent object. The idea behind inheritance is that you can create new classes that are built upon existing classes.[1] or specifying a new implementation to maintain the same behavior (realizing an interface). Such an inherited class is called a subclass of its parent class or super class. It is a mechanism for code reuse and to allow independent extensions of the original software via public classes and interfaces. The relationships of objects or classes through inheritance give rise to a directed graph. Inheritance was invented in 1967 for Simula.[2] The term "inheritance" is loosely used for both class-based and prototype-based programming, but in narrow use is reserved for class-based programming (one class inherits from another), with the corresponding technique in prototype-based programming being instead called delegation (one object delegates to another).