with Ada.Text_IO;  use Ada.Text_IO;

procedure chariteration is
  S : string(1..1);
begin
  --for c in 'A'..'Z' loop
  --for c in Character('A')..Character('Z') loop
  for c in Character'('A')..Character'('Z') loop
    S(1) := c;
    Put(S);
  end loop;
  New_Line;
end chariteration;