In object oriented languages such as C++ or Java, how are user defined exceptions typically created?

Introduction / Context:
Error handling in object oriented programming often uses exceptions. While languages provide a set of built in exception types, applications frequently need their own custom exceptions to represent domain specific error conditions. Interview questions therefore ask how user defined exceptions are created. This checks whether you understand inheritance and the exception hierarchy in languages such as C++ and Java.

Given Data / Assumptions:

• The language supports an exception base class, such as std::exception in C++ or Exception in Java.
• Custom exceptions should integrate with the existing try catch mechanism.
• We want to follow standard practices for defining and throwing exceptions.

Concept / Approach:
To create a user defined exception, you typically define a new class that extends the appropriate base exception class. This new class may add constructors to accept custom messages or additional data, and may override methods such as what() in C++ or toString() in Java to provide more detailed error descriptions. By inheriting from the base exception type, your custom exception can be thrown and caught using the normal exception handling mechanism, and it fits naturally into the exception hierarchy.

Step-by-Step Solution:
Step 1: Identify the base exception class in the language, for example Exception in Java or std::exception in C++.Step 2: Define a new class that inherits from this base class and give it a descriptive name, such as InvalidOrderException.Step 3: Provide appropriate constructors and override methods if you want to customise the behaviour or message.Step 4: Option A describes this process: inheriting from the base exception class and optionally overriding or extending functionality.Step 5: Options B, C and D either ignore the need to inherit from an exception base type or deny the possibility of user defined exceptions altogether, so option A is correct.

Verification / Alternative check:
In Java, a typical custom exception looks like class MyException extends Exception { public MyException(String message) { super(message); } }. This class can then be thrown with throw new MyException("detail"); and caught with catch (MyException e). In C++, you might derive from std::exception and override the what() method. These patterns confirm that inheritance from the base exception class is the standard way to define user defined exceptions.

Why Other Options Are Wrong:
Option B suggests overriding a random class, which would not integrate with the language's exception mechanism unless the class extends the exception base type. Option C speaks of inheriting class functionality but does not mention the exception base class or the need to integrate with exception handling. Option D is plainly false because most object oriented languages explicitly allow user defined exception types.

Common Pitfalls:
Common mistakes include deriving custom exceptions from very general base classes when more specific ones are available, or throwing primitive values instead of proper exception objects. Another pitfall is failing to provide meaningful messages, making debugging harder. When answering exam questions, emphasise that user defined exceptions are created by inheriting from the appropriate base exception class and optionally adding specialised behaviour.

Final Answer:
By creating a new class that inherits from the base exception class and, if needed, overriding or extending its functionality.