strrev function error

Question

#include <stdio.h>
#include <string.h>

int main() {
char s[100];

printf("enter a string\n");

fgets(s,100,stdin);

strrev(s);

printf("reverse of string:%s",s);

return 0;
}

when i run the program i get error

Answer 1

strrev() is not standard library function.
So it may not be available on some compilers, for example gcc.
You should code it by yourself.