Operator overloading – Extraction & Insertion Operator C++

Stream extraction (>>) and insertion (<<) operators can be overloaded for read from keyboard and display the output. input and output to accept the user defined data.  These operator also used for writing and reading from data files.

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Example :

#include <iostream.h>

//Example of Operator  <<  >>

  class Cal

      {

           private:

              int a,b,c;

           public:

              Cal()

                   {

                        a = b = 0;

                   }

              Cal(int x, int y)

                   {

                        a = x;

                        b = y;

                   }

              friend ostream &operator<<(ostream &Write, Cal &C )

                   {

                        C.c=C.a+C.b;

                        Write<<"a = "<<C.a<<" & b =" <<C.b<<"  Sum = "<<C.c;

                        return Write;

                   }

              friend istream &operator>>(istream  &Read, Cal &C )

                   {

                        Read>>C.a>>C.b;

                        return Read;

                   }

      };

  int main()

      {

           Cal C1(10,20), C2;

           cout <<"\n\tEnter Two Nos. : ";

           cin>>C2;

           cout<<"\n\tSum of : "<<C1 << endl;

           cout <<"\n\tSum of :" <<C2 << endl;

           return 0;

      }

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#include <iostream.h>

#include <fstream.h>

//Example of File using Operator  <<  >>

  class FileOp

      {

           private:

              int roll,marks;

           public:

              FileOp()

                   {}

              friend ostream &operator<<(ostream &Write,  FileOp &FP )

                   {

                        Write<<" Roll : "<<FP.roll<<" Marks : "<<FP.marks;

                        return Write;

                   }

              friend istream &operator>>(istream  &Read, FileOp &FP )

                   {

                        Read>>FP.roll>>FP.marks;

                        return Read;

                   }

      };

  int main()

      {

           fstream f;

           f.open("aaa.txt",ios::out);

           FileOp FP1,FP2;

           cout<<"\n\tEnter Roll & Marks : " << endl;

           cin>>FP1;

           f.write((char *)&FP1,sizeof(FP1));

           f.close();

           f.open("aaa.txt",ios::in);

           f.read((char *)&FP2,sizeof(FP2));

           cout<<"Data :" << FP2 << endl;

           return 0;

      }