Tuesday, February 17, 2015
What is Exception Handling in C
While doing programming we come many across errors. Most commonly there are two types of errors, logical errors and syntactical errors. The logical errors occur due to the poor understanding of problem and on the other hand syntactical errors arise due to poor understanding of language.
Many times we face some strange or odd problems other than these two types of errors, these are known as exceptions. Exceptions are the run time unusual conditions that a program may encounter while execution. It might include conditions such as division by zero, out-of-range index, running out of memory, etc.
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So we can say that the process of handling these types of exceptional conditions is known as exception handling. This is a new feature added to ANSI C++. Today, almost all compilers support this feature.
The exception handling process includes the following four steps:
1. Find the problem (Hit the exception)
2. Inform that an error has occurred (Throw the exception)
3. Receive the error information (Catch the exception)
4. Take corrective actions (Handle the exception)
Exception Handling Mechanism
C++ exception handling mechanism consists of three keywords, try, throw and catch.
try: The keyword try is used to define a block of statements which may produce exceptions and this block is known as try block.
throw: When an exception is detected, it is thrown using a throw statement in the try block.
catch: This block catches the exception thrown by throw statement in the try block and handles it appropriately. The catch block that catches an exception must immediately come after the try block that throws the exception.
The structure of these two blocks is shown below:
. . . . . .
. . . . . .
try
{
. . . . . .
throw exception //Block of statements which detects and throws an exception
. . . . . .
. . . . . .
}
catch(type arg)
{
. . . . . . //Block of statements that handles the exception
. . . . . .
}
. . . . . .
. . . . . .
When the try block throws an exception, the program control leaves the try block and enters the catch statement of the catch block. Here exception is nothing but an object used to transmit the information about a problem. If the type of object thrown matches the arg type of the catch statement then catch block is executed for handling the exception. If they do not match, the program is aborted with the help of abort() function which is invoked by default. When no exception is detected and thrown, the control goes to the statement immediately after the catch block or we can say catch block is skipped.
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A program is given below that will explain you that how actually exception handling is done in C++.
#include<iostream>
using namespace std;
int main()
{
int x,y,z;
cout<<"Enter the values of x and y:";
cin>>x>>y;
z=x-y;
try
{
if(z!=0)
{
cout<<"Result(x/z)="<<x/z;
}
else //division by zero exception
{
throw(z); //throws int object
}
}
catch(int) //catches the exception
{
cout<<"Exception caught: z="<<z;
}
return 0;
}
Outputs of the above program is shown below:
For First Run
For Second Run
If you have any doubts then feel free to ask by commenting below. Please do share if you liked the article.
Source: E Balagurusamy
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