Exception Handling in C++

 Exception Handling 

In C++, Exception Handling is a mechanism to handle runtime errors in a structured way, so that the normal flow of the program is not terminated abruptly.

 

Exception

An exception is an abnormal condition or error that occurs during program execution.

Common Runtime Errors

• Division by zero
• Array index out of bounds
• File not found
• Memory allocation failure
• Invalid user input

---

Need

Without Exception Handling

• The program crashes suddenly
• Difficult to debug
• Error-handling code mixes with normal logic

With Exception Handling

✔ Separate error handling code
✔ Program continues execution safely
✔ Easy debugging and maintenance
✔ Improves program reliability

 

Keywords Used in Exception Handling

Keyword	Purpose
try	Code that may cause an exception
throw	Used to generate an exception
catch	Handles the exception

---

4. Basic Structure of Exception Handling

try {

    // Code that may cause an exception

    throw exception;

}

catch (exception_type e) {

    // Handling code

}

---

Working Principle (Step-by-Step)

1. Code inside the try block executes
2. If an error occurs, → throw statement executes
3. Control jumps to the matching catch block
4. The exception is handled
5. The program continues after the catch

---

Simple Practical Example

Example: Division by Zero

#include <iostream>

using namespace std;

 

int main() {

    int a, b;

    cout << "Enter two numbers: ";

    cin >> a >> b;

 

    try {

        if (b == 0)

            throw b;

        cout << "Result = " << a / b;

    }

    catch (int x) {

        cout << "\nError: Division by zero is not allowed";

    }

 

    return 0;

}

Output

Enter two numbers: 10 0

Error: Division by zero is not allowed

---

Multiple Catch Blocks

Used when different types of exceptions may occur.

Syntax

try {

    // code

}

catch (int e) {

}

catch (float e) {

}

catch (...) {

}

Example : Multiple Catch

#include <iostream>

using namespace std;

 

int main() {

    try {

        throw 10.5;

    }

    catch (int e) {

        cout << "Integer Exception";

    }

    catch (float e) {

        cout << "Float Exception";

    }

    catch (...) {

        cout << "Unknown Exception";

    }

    return 0;

}

---

Catch All Exception (catch(...))

• Handles any type of exception
• Must be written last

catch (...) {

    cout << "Some error occurred";

}

 

Throwing User-Defined Exceptions

Example : Age Validation

#include <iostream>

using namespace std;

 

int main() {

    int age;

    cout << "Enter age: ";

    cin >> age;

 

    try {

        if (age < 18)

            throw age;

        cout << "Eligible for voting";

    }

    catch (int a) {

        cout << "Not eligible for voting";

    }

 

    return 0;

}

---

Exception Handling with Functions

Example : Function Throwing Exception

#include <iostream>

using namespace std;

 

void check(int x) {

    if (x < 0)

        throw x;

    cout << "Valid Number";

}

 

int main() {

    try {

        check(-5);

    }

    catch (int e) {

        cout << "Negative number exception";

    }

    return 0;

}

---

Standard Exception Classes

C++ provides built-in exception classes in <exception> header.

Class	Description
exception	Base class
bad_alloc	Memory allocation failure
bad_cast	Invalid type casting

---

Summary

• try must be followed by at least one catch
• catch(...) must be last
• Multiple throw statements are allowed
• Exception type must match the catch parameter
• Exception handling works at runtime

 

Advantages of Exception Handling

Clean code structure
Better error management
The program does not crash
Useful for large applications

Limitations

Slight performance overhead
Not suitable for simple programs

========================================================================