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Exception Handling in C++

In this guide, we'll explore exception handling in C++, an important feature used to handle runtime errors and prevent abrupt termination of programs.

1. What is Exception Handling?​

Exception handling allows a program to detect and handle runtime errors gracefully instead of terminating unexpectedly.

C++ uses three keywords:

  • try
  • throw
  • catch

2. The try Block​

The try block contains code that may generate an exception.

Syntax:​

try {
    // code that may throw exception
}

Example:​

try {
    int age = 15;

    if(age < 18) {
        throw age;
    }
}

3. The throw Keyword​

The throw statement is used to generate an exception.

Syntax:​

throw value;

Example:​

throw 100;

This sends an exception value to the matching catch block.

4. The catch Block​

The catch block receives and handles exceptions generated by matching throw.

Syntax:​

catch(exceptionType variable) {
    // handling code
}

Example:​

catch(int x) {
    cout << "Exception caught: " << x;
}

5. Complete Example of Exception Handling​

Example:​

#include <iostream>
using namespace std;

int main() {
    int age;

    cout << "Enter age: ";
    cin >> age;

    try {
        if(age < 18) {
            throw age;
        }

        cout << "Access granted";
    }

    catch(int x) {
        cout << "Access denied. Age = " << x;
    }

    return 0;
}

Output:​

Enter age: 15
Access denied. Age = 15

6. Multiple Catch Blocks​

C++ allows multiple catch blocks to handle different exception types.

Example:​

#include <iostream>
using namespace std;

int main() {
    try {
        throw 'A';
    }

    catch(int x) {
        cout << "Integer Exception";
    }

    catch(char ch) {
        cout << "Character Exception";
    }

    return 0;
}

Output:​

Character Exception

7. User Defined Exceptions​

Programmers can create custom exception classes.

Example:​

#include <iostream>
using namespace std;

class MyException {};

int main() {
    try {
        throw MyException();
    }

    catch(MyException e) {
        cout << "Custom Exception Caught";
    }

    return 0;
}

Output:​

Custom Exception Caught

8. Catch-All Handler​

C++ provides a special handler:

catch(...)

It catches any exception type that was not handled previously.

Example:​

#include <iostream>
using namespace std;

int main() {
    try {
        throw "Runtime Error";
    }

    catch(int x) {
        cout << "Integer Exception";
    }

    catch(...) {
        cout << "Unknown Exception Caught";
    }

    return 0;
}

Output:​

Unknown Exception Caught

9. Advantages of Exception Handling​

Exception handling provides several benefits:

  • Prevents abrupt termination of programs
  • Improves readability of code
  • Separates error handling logic
  • Helps detect runtime problems
  • Makes debugging easier

10. Limitations of Exception Handling​

Although useful, exception handling also has some limitations:

  • Excessive use may affect readability
  • Improper handling can hide errors
  • Slight performance overhead may occur

Final Thoughts​

Exception handling is an important concept in C++ that helps manage runtime errors effectively.

By using try, throw, and catch, programs become safer, more maintainable, and easier to debug.