undefined reference to - own library

[ewazdomu]

Hi, I tried make simple library with one function but I already have problem with error undefined reference to `hello' and I dont know why.
main.c

  #include <stdio.h>
#include "hello.h"

int main()
{
  hello();
  return 0;
}

hello.c

#include <stdio.h>
#include "hello.h"

void hello(void)
{
  printf("Hello user 4");
}

hello.h

void hello(void);

[koothkeeper]

How are you linking it?