Why can't every class be termed as user defined data type?

Differentiate between static data members and non-static data members.

Differentiate between instance variable and class variable.

Define a class Calculate to accept two numbers as instance variables. Use the following member methods for the given purposes:

Class name — Calculate

Data members — int a, int b

Member methods:
void inputdata() — to input both the values
void calculate() — to find sum and difference
void outputdata() — to print sum and difference of both the numbers
Use a main method to call the functions.