C program to merge two files into third file

Write  a C program to merge two files into a third file(i.e., the contents of the first file followed by those of the second are put in the third file).

program:

#include<stdio.h>

#include<stdlib.h>

void main()

{

FILE *f1,*f2,*f3; char s[100];

f1=fopen("D:\file3.txt","r");

f2=fopen("D:\file4.txt","r");

f3=fopen("D:\file5.txt","w"); if(f1==NULL || f2==NULL || f3==NULL)

{

printf("error opening file"); exit(0);

}

while(fgets(s,99,f1)!=NULL)

fputs(s,f3);

while(fgets(s,99,f2)!=NULL)

fputs(s,f3);

fclose(f1);

fclose(f2);

fclose(f3);

}

output: