The following example demostrates the use of some advanced method in the Character unit. An edit box is configured to allow 2 unicode characters.

 procedure TMainForm.edtCharChange(Sender: TObject);
var
  U4: UCS4Char;
  Cat: TUnicodeCategory;
  Value: String;
begin
  Value := edtChar.Text;
 
  { Do nothing on empty edit }
  if Value = '' then
    Exit;
 
  { Note that 2 characters may represent a surrogate pair! }
  { Only allow control codes and alpha-numeric values in }
  if (not IsLetterOrDigit(Value[1])) and
     (not Character.IsControl(Value[1]) and
     (not IsSurrogate(Value[1])))
     then Exit;
 
  { Covert the entered char to UCS4 }
  U4 := ConvertToUtf32(Value, 1);
 
  { And now convert back }
  if (ConvertFromUtf32(U4) <> Value) then
    MessageDlg('Cannot happen!', mtError, [mbOK], 0);
 
  MessageDlg('The numeric value of the character is '  
    FloatToStr(GetNumericValue(Value[1])), mtInformation, [mbOK], 0);
 
  { Get the unicode category of the character }
  Cat := GetUnicodeCategory(Value[1]);
 
  MessageDlg(Format('The character "%s" category is: %s ',
    [Value[1], GetEnumName(TypeInfo(TUnicodeCategory), Ord(Cat))]),
    mtInformation, [mbOK], 0);
end;
 
procedure TMainForm.FormCreate(Sender: TObject);
begin
  { Allow two characters to be typed into
    the edit box. In case of Unicode surrogates,
    2 characters represent one real character.
  }
  edtChar.MaxLength := 2;
end;