What is abstract class?
A generic class that is used only as a template for derived classes, and
that cannot be instantiated.
Below is an instruction that describes a task, paired with an input that provides further context. Write a response that appropriately completes the request.
### Instruction: What is abstract class?
### Input: 
### Response: A generic class that is used only as a template for derived classes, and
that cannot be instantiated.