control charachter

http://donsnotes.com/tech/charsets/ascii.html

x1F
\x00 =>> null  ...

Control Characters

                    CTRL   (^D means to hold the CTRL key and hit d)
Oct  Dec Char  Hex  Key     Comments
\000   0  NUL  \x00  ^@ \0 (Null byte)
\001   1  SOH  \x01  ^A    (Start of heading)
\002   2  STX  \x02  ^B    (Start of text)
\003   3  ETX  \x03  ^C    (End of text) (see: UNIX keyboard CTRL)
\004   4  EOT  \x04  ^D    (End of transmission) (see: UNIX keyboard CTRL)
\005   5  ENQ  \x05  ^E    (Enquiry)
\006   6  ACK  \x06  ^F    (Acknowledge)
\007   7  BEL  \x07  ^G    (Ring terminal bell)
\010   8   BS  \x08  ^H \b (Backspace)  (\b matches backspace inside [] only)
                                        (see: UNIX keyboard CTRL)
\011   9   HT  \x09  ^I \t (Horizontal tab)
\012  10   LF  \x0A  ^J \n (Line feed)  (Default UNIX NL) (see End of Line below)
\013  11   VT  \x0B  ^K    (Vertical tab)
\014  12   FF  \x0C  ^L \f (Form feed)
\015  13   CR  \x0D  ^M \r (Carriage return)  (see: End of Line below)
\016  14   SO  \x0E  ^N    (Shift out)
\017  15   SI  \x0F  ^O    (Shift in)
\020  16  DLE  \x10  ^P    (Data link escape)
\021  17  DC1  \x11  ^Q    (Device control 1) (XON) (Default UNIX START char.)
\022  18  DC2  \x12  ^R    (Device control 2)
\023  19  DC3  \x13  ^S    (Device control 3) (XOFF)  (Default UNIX STOP char.)
\024  20  DC4  \x14  ^T    (Device control 4)
\025  21  NAK  \x15  ^U    (Negative acknowledge)  (see: UNIX keyboard CTRL)
\026  22  SYN  \x16  ^V    (Synchronous idle)
\027  23  ETB  \x17  ^W    (End of transmission block)
\030  24  CAN  \x18  ^X    (Cancel)
\031  25  EM   \x19  ^Y    (End of medium)
\032  26  SUB  \x1A  ^Z    (Substitute character)
\033  27  ESC  \x1B  ^[    (Escape)
\034  28  FS   \x1C  ^\    (File separator, Information separator four)
\035  29  GS   \x1D  ^]    (Group separator, Information separator three)
\036  30  RS   \x1E  ^^    (Record separator, Information separator two)
\037  31  US   \x1F  ^_    (Unit separator, Information separator one)
\177 127  DEL  \x7F  ^?    (Delete)  (see: UNIX keyboard CTRL)