Exception Handling in C++

Exception Handling in C++

• 1.
  G. H. RAISONICOLLEGE OF ENGINEERING (AN AUTONOMOUS INSTITUTE AFFILIATED BY R. T. M. NAGPUR UNIVERSITY UNDER UGC ACT 1956) DEPARTMENT OF INFORMATION TECHNOLOGY SESSION 2016-2017 Object Oriented Programming Through C++ TAE-2 Topic: exception handling in c++ Deepak tathe (37)
• 2.
  WHAT IS ANEXCEPTION ?  It is often easier to write a program by first assuming that nothing incorrect will happen  But sometimes user enters an Invalid value e.g. In a factorial program if a user enters any negative value.  For such cases Exception Handling is used.  Using Exception Handling you can easily manage and respond to run-time error.
• 3.
  COMMON FAILURES  newnot allocating memory  Division by zero  Invalid function parameters  C does not have Exception Handling Mechanism  But, C++ have build in Exception Handling Mechanism  We can handle exception without exception handling but that will not be a professional and systematic approach and it will not clear the program logic.
• 4.
   In Exceptionhandling we use three keywords try , catch, throw.  Program statements you want to monitor for exceptions are contained in a try box  If an exception occurs within the try block it is thrown  The exception is caught using Catch and processed. Try , Catch , Throw
• 5.
  RELATING EXCEPTION HANDLINGWITH REAL LIFE If a Smartphone fails the test try throw catch
• 6.
  IMPORTANT POINTS  Whena try block end it must be followed by a catch block.  If we write catch block but don’t write try block then the program will show  If we don’t write try and catch but write throw then the program will build and run but it will show run time error. #include<iostream> main() { std::cout<<"welcome"; throw 10; return 0; }
• 7.
  TRY BLOCK  Inan program a block of code which can produce error is placed in try block  When an exception is detected in try it is thrown using throw statement  Syntax try { throw exception; } catch(type argument) { }
• 8.
  #include<iostream> using namespace std; main() { inta,b; cout<<"enter values of a and bn"; cin>>a; cin>>b; int x=a-b; try{ if (x!=0) { cout<<"result(a/x)="<<a/x<<"n"; } else{ throw(x); } } catch(int i) { cout<<"exception caught:x="<<x<<"n"; } cout<<"end"; return 0; }
• 9.
  THROWING MECHANISM  Anexception is thrown using the throw statement in one of the following ways throw(exception); throw exception; throw; o We can add use multiple throw statements by using if – else statement e.g. int i=3; Try { if(i==1) throw 1; if(i==2) throw 2; }
• 10.
  CALL THROW USINGFUNCTION #include<iostream> using namespace std; void fun() { throw 3; } int main() { int i=3; try{ if (i=3) fun(); } catch(int e){ cout<<"n exception no:"<<e; } cout<<"n throw successfully called by function"; getch(); } fun function contains throw In try instead of writing throw fun function is calling throw
• 11.
  CATCHING MECHANISM  Acatch block look like a function definition and is of the form Catch (type arg) { // statements for managing exceptions }  The type indicates which type of exception that catch block handles  The catch statement catches an exception whose type matches with the type of catch argument. When it is caught the code in the catch block is executed  Due to mismatched, if an exception is not caught, abnormal program termination will occur  The catch block is simply skipped if the catch statement does not catch an exception
• 12.
  MULTIPLE CATCH STATEMENT Syntax for multiple catch statement
• 13.
  MULTIPLE CATCH  Inmultiple catch when an exception is thrown the exception handlers are searched in order of an appropriate match  When no match is found the program is terminated  It is possible that arguments of several catch statement match the type of an exception in such cases the first handler that matches the exception is executed
• 14.
  CATCH ALL EXCEPTION One catch statement can catch all exception instead of a certain type alone.  This could be done by defining the catch statements using ellipse as follows catch (…) { // statements for processing // all exceptions }