In this article we are going to see what is Open Closed Principle (OCP) in SOLID. OCP is open for extension and closed for modification. that means a class can be extended through override and not allow to modify.
we see Employee class in which GetSalary is used to fetch the salary this method can be override in Manager class which is derived from employee class but not allow to modify the employee class.
From this article you can learn the Open Closed Principle