[user02@FC4 Lesson08]$ cat -n use_not.c

   1  #include <stdio.h>
   2
   3  int main(void)
   4  {
   5     int user_owns_a_dog = 0;
   6     int user_owns_a_cat = 1;
   7
   8     if (! user_owns_a_dog)
   9        printf("You should buy a dog\n");
  10
  11     if (! user_owns_a_cat)
  12        printf("You should buy a cat\n");
  13
  14     return 0;
  15  }

[user02@FC4 Lesson08]$ gcc -o use_not use_not.c
[user02@FC4 Lesson08]$ ./use_not
You should buy a dog