Answer to Quiz 6(b) Thu 4 Oct 2001

1. We say that a letter lies in the first half of the alphabet
   if the letter is in the range 'a'..'n' or in 'A'..'N'.

   The function first_half has prototype

     int first_half ( char c );
     /* returns 1 if c is in the range 'a'..'n' or 'A'..'N';
        returns 0 otherwise  */

So first_half('g') returns 1, while first_half('r') returns 0.
Write the definition of first_half below :


     int first_half ( char c )
     {
        if ((('a' <=  c) && (c <= 'n'))
         || (('A' <=  c) && (c <= 'N')))
           return 1;
        else
           return 0;
     }

2. Write a program that replaces every control character in the input by a
   single space.  Typically, the program is run as a.out < input.

   Use iscntrl() from ctype.h.


        #include <stdio.h>
        #include <ctype.h>

        int main(void)
        {
           int c;
          
           while ((c = getchar()) != EOF)
              if (iscntrl(c)) 
                 putchar(' ');
              else 
                 putchar(c);

           return 0;
        }