#include <stdio.h>
#include <stdlib.h>

int main(int argc, char* argv[]){
#define fn "data1.txt"
#define gn "data2.txt"

FILE *f, *g;
f= fopen(fn, "r"); g= fopen(gn,"r");
if( f==NULL){
printf("NG:%s\n",fn); exit(-1);
}
g= fopen(gn, "r");
if( g==NULL){
printf("NG:%s\n",gn); exit(-1);
}
int cf, cg;
while( (cf= fgetc(f))!=EOF &&
(cg= fgetc(g))!=EOF ){
if( cf!=cg ) break;
}
printf("\n");
printf("cf: "); if(cf==EOF)printf("EOF\n");else printf("%c\n",cf);
printf("cg: "); if(cg==EOF)printf("EOF\n");else printf("%c\n",cg);

if( !(cf==EOF && fgetc(g)==EOF) )
printf("%s and %s differ.\n", fn,gn);
fclose(f); fclose(g);

return 0;
}