Amit Mishra

• Mar 21st, 2006

 

RTTI is a compiler was developed by microsoft with the help of visual C which work is, if we don't declared datatype to particular variable, then this compiler take defaultly the datatype of the variable according to the data defined to it. E.g. if we write only#include "stdio.h"void main() { x=5; y=6.9; z= 'A'; . . .. }Then compiler takes defaultly x as integer, y is float & z is char types.

mohit12379

 Profile Answers by mohit12379 Questions by mohit12379

• Apr 20th, 2006

 

Run-time type information (RTTI) is a mechanism that allows the type of an object to be determined during program execution. RTTI was added to the C++ language because many vendors of class libraries were implementing this functionality themselves. This caused incompatibilities between libraries. Thus, it became obvious that support for run-time type information was needed at the language level.

There are three main C++ language elements to run-time type information:

1)The dynamic_cast operator. :- Used for conversion of polymorphic types.
 
  class B { ... };
  class C : public B { ... };
  class D : public C { ... };
 
  void f(D* pd)
  {
     C* pc = dynamic_cast<C*>(pd);// ok: C is a direct base class
                                  // pc points to C subobject of pd
 
     B* pb = dynamic_cast<B*>(pd);// ok: B is an indirect base class
                                  // pb points to B subobject of pd
     ...
  }
---------------------------------------------------------------------------
2)The typeid operator :- Used for identifying the exact type of an object.
                       
3)The type_info class :- Used to hold the type information returned by the typeid operator.The type_info class describes type information generated within the program by the compiler.
 
NOTE:-   TRY THIS EXAMPLE IS COMPILE AND LINK USING MSVC++ 6.0 CL.EXE Compiler and Linker  PLS CHECK SAME typid available in UNIX based C++;
 **************************************************************************************                       
 #include "stdio.h"
 #include <typeinfo.h>
 
 class A
 {
 public:
 };
 
 class B:public A
 {
 public:
 };
 
 int main(int argc, char* argv[])
 {
    int   iVal = int();
    float fVal = float();
    char  cVal = char();
    A a,a1;
    B b;
 
    const type_info& t_iVal = typeid(iVal);      // Holds Simple int DataType Info
    const type_info& t_iValRef = typeid(&iVal);  // Holds pointer type_info
    printf("\n Type Info of  iVal = %s\n",t_iVal.name());
    printf("\n Type Info of &iVal = %s\n",t_iValRef.name());
 
    printf("\n Type Info of fVal = %s\n",typeid(fVal).name());
    printf("\n Type Info of &fVal = %s\n",typeid(&fVal).name());
 
    printf("\n Type Info of cVal = %s\n",typeid(cVal).name());
    printf("\n Type Info of &cVal = %s\n\n",typeid(&cVal).name());
 
    printf("\n Type Info of a = %s\n",typeid(a).name());
    printf("\n Type Info of b = %s\n\n",typeid(b).name());
 
    if(typeid(a) == typeid(a1))
    {
     printf("\n BOTH INSTANCES a AND a1 BELONGS TO SAME CLASS \n\n");
    }
 
    return 0;
}
*****************************************************************************************
                         
                        

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