Задачка со scanf() printf(), взято с http://www.gowrikumar.com/c/ Опции

[sigmaN]

What is the differnce between the following function calls to scanf?(Please notice the space carefully in the second call. Try removing it and observe the behaviour of the program)

Код

#include <stdio.h>
  int main()
  {
      char c;
      scanf("%c",&c);
      printf("%c\n",c);

      scanf(" %c",&c);
      printf("%c\n",c);

      return 0;
  }

Почему без пробела не работает?