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

   1  #include <iostream>
   2  using namespace std;
   3
   4  int main()
   5  {
   6     int user_owns_a_dog = 0;
   7     int user_owns_a_cat = 1;
   8
   9     if (! user_owns_a_dog)
  10        cout << "You should buy a dog" << endl;
  11
  12     if (! user_owns_a_cat)
  13        cout << "You should buy a cat" << endl;
  14
  15     return 0;
  16  }

[user02@FC4 Lesson08]$ g++ -o use_not use_not.cpp
[user02@FC4 Lesson08]$ ./use_not
You should buy a dog