Program to read decimal numbers from a file and convert into hexadecimal

# include <iostream.h>
# include <fstream.h>
# include <string.h>
# include <stdlib.h>
# include <conio.h>

 void hexadecimal(long);

 int main( )
    {
       clrscr( );

       fstream file(\"CP-01.txt\",ios::in|ios::nocreate);

       if(!file)
      {
         cout<<\"\\n Unable to open the input file.\"<<endl;
         cout<<\"\\n Press any key to exit.\";

         getch( );
         exit(EXIT_FAILURE);
      }

       long decimal_number=0;

       char Decimal_number[10]={NULL};

       do
      {
         strset(Decimal_number,NULL);

         file.getline(Decimal_number,6);

         decimal_number=atol(Decimal_number);

         if(decimal_number==0)
        break;

         hexadecimal(decimal_number);
      }
       while(1);

       file.close( ); 

       getch( );
       return 0;
    }


 //--------------------------  hexadecimal(long) -------------------------//


 void hexadecimal(long number)
    {
       int qutiont=0;
       int remainder=0;

       char Hex_digit[5]={NULL};
       char Hexadecimal_number[10]={NULL};

       do
      {
         qutiont=number/16;
         remainder=number%16;
         number=qutiont;

         if(remainder<10)
        {
           strset(Hex_digit,NULL);

           itoa(remainder,Hex_digit,10);

           strcat(Hexadecimal_number,Hex_digit);
        }

         else
        {
           switch (remainder)
              {
             case 10 : strcat(Hexadecimal_number,\"A\");
                   break;
             case 11 : strcat(Hexadecimal_number,\"B\");
                   break;

             case 12 : strcat(Hexadecimal_number,\"C\");
                   break;

             case 13 : strcat(Hexadecimal_number,\"D\");
                   break;

             case 14 : strcat(Hexadecimal_number,\"E\");
                   break;

             case 15 : strcat(Hexadecimal_number,\"F\");
                   break;
              }
        }
      }
       while(number>0);

       strrev(Hexadecimal_number);

       cout<<Hexadecimal_number<<endl;
    }