why the implicit call to EXIT() and clrscr() are marked as error ?

please have a look at my code , and there are errors as per the codechef's compiler !

include<stdio.h>

void f1(); void f1() { int x; scanf("\n%d",&x); if(x!=42) { printf("%d\n",x); { f1(); } } else { exit(); }

}

int main() {

clrscr(); f1(); getch(); return 0; }