i wrote a c program to compare two text file and write it to a new text file but the third text file is not open!

/* Here is my code. please check it and reply me(e-mail)  where is/are the mistake i have created! */

#include<stdio.h>
#include<conio.h>
#include<io.h>


void main()
{

   FILE *f1, *f2, *f3;
   char ch1,ch2;

   clrscr();
   f1 = fopen("a.txt","r");
   if(f1 == NULL)
   {
	printf("Cannot open first file\n");
   }
   else
   {
	printf("a file is opened.\n");
   }


   f2 = fopen("b.txt","r");
   if(f2==NULL)
      {
	printf("Cannot open second file\n");
	getch();
	exit(1);
      }
   else
   {
	printf("b file is opened.");
   }

   printf("Here we ready!");

   f3 = fopen("c.txt","w");
   if(f3==NULL)
   {
	printf("file is not created!");
	exit(1);
   }
   else
	printf("\nfile three is created\n");
   while(f1!=NULL && f2!=NULL)
   {
      ch1 = getc(f1);
      ch2 = getc(f2);
      if(ch1==ch2)
      {
	putc(ch2,f3);
	continue;
      }
      else
      {
	 printf("\n char1 = %c and char = %c",ch1,ch2);
	 getch();
	 exit(1);
      }
   }          fflush(stdin);
  // ch2='\0';
   //putc(ch2,f3);
   fclose(f3);
   printf("\n Work completed!");
   getch();
   fclose(f1);
   fclose(f2);
}