Changing Case of char Array

Using Arduino Programming Questions
10

GoForSmoke:

  while (*ch) // exits on terminating NULL

{
    if (( *ch & 0xDF >= 'A' ) && ( *ch & 0xDF <= 'Z' ))  *ch &= 0xDF; // so that bit 5 only gets cleared for alphas

// this was left as an exercise for the student
    ch++;
  }