What is Exception Handling?

An exception is an error that arises during the execution of a program. In C++, the exception is an event which is occurred at the runtime.
The exceptions are derived from std::exception class. It is a runtime error which can be handled and if they are not handled then the exception prints exception message and terminate the program.
In C++, the exception handling consists of three keywords: try, catch and throw.

Let us discuss them:

Try:

The try block identifies a block of code which can throw the exception. There can be one or more catch blocks after a try block.

Catch:

The catch block identifies the block of code that is executed when a particular exception is thrown. The program catches the exception with an exception handler at the place in a program where you want to handle the problem.

Throw:

It is used to throw an exception and it is also used to show those exceptions that a function throws which cannot be handled by them.

Let us have a look at the syntax:

try {

// protected code

} catch( ExceptionName e1 ) {

// catch block

} catch( ExceptionName e2 ) {

// catch block

} catch( ExceptionName eN ) {

// catch block

}

Let us have a look at the example:

#include <iostream> 

using namespace std; 

float division(int x, int y) { 

   if( y == 0 ) { 

      throw "Division not possible"; 

   } 

   return (x/y); 

} 

int main () { 

   int i = 25; 

   int j = 0; 

   float k = 0; 

   try { 

      k = division(i, j); 

      cout << k << endl; 

   }

   catch (const char* e) { 

      cout << e << endl; 

   } 

   return 0; 

}

#include <iostream>

using namespace std;

float division(int x, int y) {

if( y == 0 ) {

throw "Division not possible";

}

return (x/y);

}

int main () {

int i = 25;

int j = 0;

float k = 0;

try {

k = division(i, j);

cout << k << endl;

}

catch (const char* e) {

cout << e << endl;

}

return 0;

}

What is the advantage of using Exception?

It helps programmers to create reliable systems.
Functions can handle only the exceptions they choose i.e., a function can throw many exceptions, but may choose handle only some of them.
We can handle the exceptions outside the regular code by throwing the exceptions from a function definition or by re-throwing an exception.
It helps to separate the exception handling code from the main logic of program.

Standard Exceptions in C++

In C++, it provides a list of standard exceptions which are defined in <exception> which we can use in our programs and they are arranged in a parent-child class hierarchy.