include \cxpl\codesi;
int     C;
repeat  C:= Chin(1);
        Chout(0, C + (if C>=^A & C<=^M ! C>=^a & C<=^m then 13
                  else if C>=^N & C<=^Z ! C>=^n & C<=^z then -13
                  else 0))
until   C = $1A