Exception Handling in C++ using Try–Catch

Abstract

In C++, runtime errors can cause abnormal program termination. Exception handling provides a structured way to detect and manage such errors. This blog explains the concept of try–catch blocks, throw keyword, types of exceptions, and best practices, with simple examples suitable for NIT / GATE / university exams.

---

1. Introduction

Errors in a program are broadly classified into:

• Compile-time errors

• Run-time errors

• Logical errors

Run-time errors such as division by zero, invalid memory access, or file handling issues cannot always be detected during compilation.
To handle such errors safely, C++ provides exception handling.

---

2. What is Exception Handling?

An exception is an abnormal condition that occurs during program execution.
Exception handling allows the program to:

• Detect the error

• Transfer control to a handler

• Continue execution safely

C++ uses three keywords:

• try

• throw

• catch

---

3. Syntax of Try–Catch

try {
    // code that may generate exception
}
catch (exception_type e) {
    // handling code
}

---

4. Working Mechanism

1. Code inside try block is executed.

2. If an error occurs, throw is executed.

3. Control jumps to the matching catch block.

4. Remaining code executes normally.

---

5. Simple Example: Division by Zero

#include <iostream>
using namespace std;

int main() {
    int a = 10, b = 0;

    try {
        if (b == 0)
            throw b;
        cout << a / b;
    }
    catch (int x) {
        cout << "Error: Division by zero";
    }

    return 0;
}

Output

Error: Division by zero

---

6. Multiple Catch Blocks

Different exceptions can be handled separately.

try {
    throw 3.5;
}
catch (int e) {
    cout << "Integer exception";
}
catch (double e) {
    cout << "Double exception";
}

---

7. Catch-All Handler

Used when the type of exception is unknown.

try {
    throw 'A';
}
catch (...) {
    cout << "Unknown exception occurred";
}

---

---

9. Throwing Exceptions from Functions

void check(int x) {
    if (x < 0)
        throw x;
}

int main() {
    try {
        check(-5);
    }
    catch (int e) {
        cout << "Negative value error";
    }
}