Exception_Handling_in_C__1701342048430.ppt

Exceptions
• Run time errors that a program may encounter while
executing.
• Example
– Divide by Zero
– Access elements out of size
Drawbacks
• Abnormal program termination when the exception
occurs.
• The user can not find where the exception occurs.

Exception Handling
• Is a mechanism of detecting and reporting
exceptional circumstance so that an
appropriate action can be taken.
• To transmit information about the problems.
Task
• Find the problem(Hit the exception-Try)
• Send the error information(Throw the
exception)
• Receive the error information(Catch the
exception)
• Take corrective actions.(handle the exception)

Exception handling mechanism is done using
Try
Is a block of statement which may generate
exceptions.
try{}
Catch
Is a block which catches and handles exception by
taking appropriate actions.
catch(datatype arg){}
Throw
Is a statement , to throw the detected exception to
catch block.
throw exception;

• Throwing Mechanism
– throw(exception)
– throw exception
– throw //Rethrowing exception- used to rethrow
the exception caught without processing it.
– exceptions are variable of any type.
– It should be caught by catch block which matches the
argument.

Multiple catch statement
try
{}
catch(arg)
{}
catch(arg)
{}
catch(arg)
{}

Catch all exceptions
Not possible to for the design of
independent catch handlers.
catch(...){} //called default catch to catch
all exceptions.

#include<iostream>
using namespace std;
int main()
{
int a,b,c;
cout<<"enter values";
try{
cin>>a>>b;
if(a<0 && b<0)
throw 0;
else if(b==0)
throw('x');
else{
c=a/b;
cout<<c<<endl;}}
catch(int n)
{
cout<<"enter positive values";
}
catch(char c)
{
cout<<"enter non zero value";
return 0;
}
}
Exception Handling-multiple catches

#include<iostream>
int bsquare(int a)
{
try{
if(a==0)
throw 1;
else if(a<0)
throw 3.14f;
else
return (a*a);
}
catch(int s)
{
cout<<"enter non zero value";
}
catch(float f)
{
throw; //Rethrowing Exception
}}
int main()
{
int x;
cin>>x;
try{
cout<<bsquare(x);
}
catch(...) //Default Catch
{
cout<<"Rethrouing exception caught"<<endl;
}
}

Exception Class
class Exclass
{
};
try
{
throw Exclass(args);
}
catch(Exclass obj)
{
}

Exception Class-user defined exception
#include<iostream>
class Bexception
{
int ecode;
string emsg;
public:
Bexception(int a,string s)
{
ecode=a;
emsg=s;
}
void display()
{
cout<<ecode<<" : "<<emsg<<endl;
}
};
int main()
{
int x;
cin>>x;
try{
if(x==0)
throw Bexception(1000,"Zero value
exception");
else
cout<<(x*x);
}
catch(Bexception B)
{
B.display();
}
catch(...)
{
cout<<"Rethrouing exception
caught"<<endl;
}
}

Programs
Create a class namely “stack” demonstrate the
following
• Stack overflow exception
• Stack underflow exception
• Empty stack exception while trying to pop before doing
push
• To handle rethrown exception.
Create a class namely “average” demonstrate the
following
• Divide by zero exception
• Negative value exception
• Default exception
• To handle rethrown exception.

class Bstack
{
private:
int st[3];
int top,flag;
public:
Bstack()
{
top=0;flag=0;
}
int pop()
{
try{
if(flag==0)
throw 3.14f;
top--;
if(top<0)
throw('c');
else
return st[top];
}
catch(char c)
{
cout<<"Stack Under flow
Exception"<<endl;
}
catch(float ff)
{
cout<<"empty stack
exception"<<endl;
throw; }}};
main()
{
Bstack B;
try{
B.pop();}
catch(...)
{
cout<<"Rethrowing
Exception"<<endl;}
B.push(20);
B.push(30);
B.push(40);
B.push(50);
cout<<B.pop()<<endl;
}
void push(int n)
{
flag=1;
try{
if(top>=3)
throw(0);
else
{
st[top]=n;
top++;}
}
catch(int z)
{
cout<<"Stack overflow
exception"<<endl;
}
}

[bavani@mepcolinux ~]$./a.out
empty stack exception
Rethrowing Exception
Stack overflow exception
40
30
20
Stack Under flow Exception
0

class Average
{
int a[100],n;
public:
void get()
{
cout<<"Enter N";
try{
cin>>n;
if(n==0)
throw 10;
else
{
cout<<"Enter Values";
for(int i=0;i<n;i++)
{
cin>>a[i];
}
}
}
catch(int s)
{
cout<<"Divide by Zero Exceptionn";
throw;
}
}
void average()
{
int sum=0;
try{
for(int i=0;i<n;i++)
{
if(a[i]<0)
throw 3.14f;
else
sum=sum+a[i];
}
}
catch(float ff)
{
cout<<"Negative value Exceptionn";
throw;
}
}
};

int main()
{
Average A;
L1:
try{
A.get();
A.average();
}
catch(int nn)
{
cout<<"Rethrowing Exception in Mainn";
goto L1;
}
catch(...)
{
cout<<"Default Catchn";
}
}
[bavani@mepcolinux ~]$./a.out
Enter N0
Divide by Zero Exception
Rethrowing Exception in main
Enter N3
Enter Values1
2
-3
Negative value Exception
Default Catch

Exception_Handling_in_C__1701342048430.ppt

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Exception_Handling_in_C__1701342048430.ppt