Listing 2: dcdr.c

/* program dcdr.c */

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

main()

{

 char ch;
 int offset;

 do {
  ch = getchar();
  if (ch <= 79 && ch >= 33) {
   offset = 79 - ch + 1;
   ch = 79 + offset;
  } /* end then */ 
  else {
   if (ch >= 80 && ch <= 126) {
    offset = ch - 80 + 1;
    ch = 80 - offset;
   } /* end then */ 
  } /* end else */
  if (isupper(ch))
   ch = tolower(ch);
  else {
   if (islower(ch))
    ch = toupper(ch);
  } /* end else */
  if (ch != 0xff)
   putchar(ch);
 } while (!feof(stdin));

} /* end main */

/* end program dcdr.c */
