1. What is an Abstract Class?
An abstract class is a partially implemented class.
It can have both abstract methods (no body) and normal methods (with body).
2. Key rule
An abstract class cannot be instantiated
It must be inherited by another class
3. What can an abstract class contain?
Abstract methods
Non-abstract (normal) methods
Fields
Properties
Constructors
4. Syntax example (interview-friendly)
abstract class Employee
{
public abstract void Work();
public void Login()
{
// common code
}
}
class Developer : Employee
{
public override void Work()
{
// implementation
}
}
5. Method implementation rule
Abstract methods must be overridden in the derived class
Normal methods are optional to override
6. Inheritance rule
Supports single inheritance only
Multiple inheritance is not allowed with classes
7. Abstract class vs Interface (short point)
Abstract class → Partial abstraction
Interface → Complete abstraction
8. Why do we use abstract classes?
To share common base functionality
To enforce base rules with flexibility
When some behavior is common and some is different
9. Important interview one-liner
An abstract class provides a base class with both implemented and unimplemented methods.