In C++ exception handling, which operator or syntax is used to declare a catch all handler that can catch any type of exception?

Introduction / Context:
C++ supports multiple catch blocks to handle different exception types. Sometimes, you want a catch block that will handle any exception that was not caught by earlier, more specific handlers. This is called a catch all handler and uses a distinctive syntax in the language.

Given Data / Assumptions:

• We are using try and catch blocks in C++.
• We want a catch that can handle exceptions of any type.
• We are asked about the operator or syntax used for this generic handler.

Concept / Approach:
A catch all handler in C++ is declared using catch(...) with three dots inside the parentheses. The three dots are called an ellipsis. This handler must appear after more specific catch blocks and will handle any exception that reaches it, regardless of type. It is typically used for logging, cleanup, or providing a generic error message when the exact exception type is not important.

Step-by-Step Solution:
Step 1: Recall the general structure: try { /* code */ } catch(Type1 &e) { /* handle */ } catch(...) { /* catch all */ }. Step 2: Note that the final catch uses three dots in the parentheses, indicating that it does not specify any particular type. Step 3: The three dots are known as an ellipsis in C++ syntax. Step 4: Therefore, the operator or syntax used for a catch all handler is the ellipsis operator '...'. Step 5: Match this with the option labelled ellipsis operator.

Verification / Alternative check:
You can verify by writing code that throws different types of exceptions, such as int, std::runtime_error, and custom exception classes. If you provide only catch(...) after the try block, it will handle all of them. Replacing catch(...) with a specific type such as catch(std::exception &) will no longer catch non std::exception types, confirming that catch(...) is indeed the universal handler.

Why Other Options Are Wrong:
Option B, the ternary operator ?:, is used for conditional expressions, not exception handling. Option C, string operator, is not a standard C++ term. Option D, unary operator, refers to operators that operate on a single operand (like ++ and --), which have nothing to do with catch all handlers.

Common Pitfalls:
A common mistake is to rely only on catch(...) and skip more specific handlers, which can hide useful information about the nature of errors. Another pitfall is placing catch(...) before specific catch blocks; it must always come last, otherwise it will consume all exceptions and prevent specific handlers from running. Used carefully, the ellipsis based catch block is a helpful safety net for unexpected errors.

Final Answer:
The catch all handler in C++ uses the ellipsis operator (...) in catch(...), so the correct option is ellipsis operator.