Exercise 1-6

Exercise 1-6  Verify that the expression getchar() != EOF is 0 or 1.

I can run the following program and feed it input like this:
# ./a.out < prog.c

#include <stdio.h>

int main(void)

{

  int c;

  int zero = 0, one = 0, other = 0;

  do

  {

    switch ((c=getchar())!=EOF)

    {

      case 0:

        zero=1;

        break;

      case 1:

        one=1;

        break;

      default:

        other=1;

        break;

    }

  }

  while (c != EOF);

  if (zero)

    printf ("The expression evaluated to 0 at least once.\n");

  if (one)

    printf ("The expression evaluated to 1 at least once.\n");

  if (other)

    printf ("The expression evaluated to an unexpected result at least once.\n");

  return 0;

}