Handling the Unexpected

In old-school C, if you divided by zero or ran out of memory, your program simply crashed with no explanation. C++ provides a structured way to gracefully catch and recover from errors using Exceptions.

The Three Key Keywords

1. try: Wrap the block of code that might fail.
2. throw: Manually trigger an error "signal" if something goes wrong.
3. catch: Handle the signal and prevent the crash.

try {
    if (age < 18) throw 505; // Throw an error code
} catch (int errorCode) {
    cout << "Access denied. Error: " << errorCode;
}

The Standard Library Exceptions (<stdexcept>)

C++ has a built-in hierarchy of common error types:

• out_of_range: You tried to access index 10 of a 5-item array.
• invalid_argument: You passed bad data to a function.
• bad_alloc: The computer is completely out of memory.

Why use Exceptions?

They allow you to separate your "Normal Logic" from your "Error Handling Logic." This makes your code much cleaner and easier to read. Instead of checking if(error) after every single line, you just wrap the whole process in one try block.

The "Catch-All" Block

catch (...) {
    cout << "An unknown disaster occurred!";
}

Never let an exception escape from a Destructor. If an exception is thrown while the system is already cleaning up after another exception, C++ will instantly kill your program with no chance for recovery.