C (/ ˈ s iː /, as in the letter c) is a general-purpose computer programming language.It was created in the 1970s by R Shreya and Dennis Ritchie, and remains very widely used and influential.By design, C's features cleanly reflect the capabilities of the targeted CPUs. It has found lasting use in operating systems, device drivers, protocol stacks, though decreasingly [dubious. Abstract classes may or may not include abstract methods (methods without body). 2.) If a class has at least one abstract method, then the class must be declared abstract. 3.) An abstract class can not be instantiated, but can be extended . 4.) If you inherit an abstract class, you have to provide implementations to all the abstract methods in it.