Exception Handling: C plus plus Class Notes

Updated: Aug 18

Mobiprep has created class notes for all C++ and templates to help you with the revision of concepts for your examinations. So let’s get started with the notes on C++.

  1. Basics of C plus plus

  2. Basics Of OOPs

  3. Classes and Objects

  4. Polymorphism and Inheritence

  5. Exception Handling

  6. File Handling and templates

We have curated a list of the most important questions asked in universities such as BITS, NSIT, VIT, IIIT, IP, Pune University, Manipal University, and many more. The questions are created from the previous year's question papers of colleges and universities.

  1. Compare and contrast error and exception.

  2. What is a user defined exception. Write down the scenario where we require user defined exceptions.

  3. When do we need multiple catch blocks for a single try block? Give an example.

Exception Handling


Question 1) Compare and contrast error and exception.

Answer) Exceptions are those which can be handled at the run time whereas errors cannot be handled.

An exception is an Object of a type deriving from the System. Exception class. System Exception is thrown by the CLR (Common Language Runtime) when errors occur that are nonfatal and recoverable by user programs. It is meant to give you an opportunity to do something with throw statement to transfer control to a catch clause in a try block.


Exception syntax:

try
{
//write your code here
}
Catch (exception type)
{
//writ your code here
}


An Error is something that most of the time you cannot handle it. Errors are unchecked exception and the developer is not required to do anything with these. Errors normally tend to signal the end of your program, it typically cannot be recovered from and should cause you exit from current program. It should not be caught or handled.


All the Errors are Exceptions but the reverse is not true. In general Errors are which nobody can control or guess when it happened, on the other hand Exception can be guessed and can be handled.


 

Question 2) What is a user defined exception. Write down the scenario where we require user defined exceptions.

Answer) Let's see the simple example of user-defined exception in which std::exception class is used to define the exception.

#include <iostream>
#include <exception>
using namespace std;
class MyException : public exception{
public:
const char * what() const throw()
{
return "Attempted to divide by zero!\n";
}
};
int main()
{
try
{
int x, y;
cout << "Enter the two numbers : \n";
cin >> x >> y;
if (y == 0)
{
MyException z;
throw z;
}
else
{
cout << "x / y = " << x/y << endl;
}
}
catch(exception& e)
{
cout << e.what();
}
}


Output:

Enter the two numbers :
10
2
x / y = 5

 

Question 3) When do we need multiple catch blocks for a single try block? Give an example.

Answer) Multiple catch blocks are used when we have to catch a specific type of exception out of many possible type of exceptions i.e. an exception of type char or int or short or long etc. Let's see the use of multiple catch blocks with an example.


Example:

#include<iostream>

using namespace std;

int main()
{
int a=10, b=0, c;
try
{
//if a is divided by b(which has a value 0);
if(b==0)
throw(c);
else
c=a/b;

}
catch(char c) //catch block to handle/catch exception
{
cout<<"Caught exception : char type ";
}
catch(int i) //catch block to handle/catch exception
{
cout<<"Caught exception : int type ";
}
catch(short s) //catch block to handle/catch exception
{
cout<<"Caught exception : short type ";
}
cout<<"\n Hello";
}


Output :

Caught exception : int type
Hello






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