The 33 ASCII control characters (codes 0–31 and 127) are non-printable characters originally designed to control hardware devices like printers and teleprinters. They include communication control codes, device control signals, and data formatting characters.
| DEC | OCT | HEX | BIN | Symbol | HTML | Description |
|---|---|---|---|---|---|---|
| 0 | 000 | 0x00 | 00000000 | NUL | � | Null character |
| 1 | 001 | 0x01 | 00000001 | SOH |  | Start of Heading |
| 2 | 002 | 0x02 | 00000010 | STX |  | Start of Text |
| 3 | 003 | 0x03 | 00000011 | ETX |  | End of Text |
| 4 | 004 | 0x04 | 00000100 | EOT |  | End of Transmission |
| 5 | 005 | 0x05 | 00000101 | ENQ |  | Enquiry |
| 6 | 006 | 0x06 | 00000110 | ACK |  | Acknowledge |
| 7 | 007 | 0x07 | 00000111 | BEL |  | Bell, Alert |
| 8 | 010 | 0x08 | 00001000 | BS |  | Backspace |
| 9 | 011 | 0x09 | 00001001 | HT | 	 | Horizontal Tab |
| 10 | 012 | 0x0A | 00001010 | LF | | Line Feed |
| 11 | 013 | 0x0B | 00001011 | VT |  | Vertical Tabulation |
| 12 | 014 | 0x0C | 00001100 | FF |  | Form Feed |
| 13 | 015 | 0x0D | 00001101 | CR | | Carriage Return |
| 14 | 016 | 0x0E | 00001110 | SO |  | Shift Out |
| 15 | 017 | 0x0F | 00001111 | SI |  | Shift In |
| 16 | 020 | 0x10 | 00010000 | DLE |  | Data Link Escape |
| 17 | 021 | 0x11 | 00010001 | DC1 |  | Device Control 1 (XON) |
| 18 | 022 | 0x12 | 00010010 | DC2 |  | Device Control 2 |
| 19 | 023 | 0x13 | 00010011 | DC3 |  | Device Control 3 (XOFF) |
| 20 | 024 | 0x14 | 00010100 | DC4 |  | Device Control 4 |
| 21 | 025 | 0x15 | 00010101 | NAK |  | Negative Acknowledge |
| 22 | 026 | 0x16 | 00010110 | SYN |  | Synchronous Idle |
| 23 | 027 | 0x17 | 00010111 | ETB |  | End of Transmission Block |
| 24 | 030 | 0x18 | 00011000 | CAN |  | Cancel |
| 25 | 031 | 0x19 | 00011001 | EM |  | End of Medium |
| 26 | 032 | 0x1A | 00011010 | SUB |  | Substitute |
| 27 | 033 | 0x1B | 00011011 | ESC |  | Escape |
| 28 | 034 | 0x1C | 00011100 | FS |  | File Separator |
| 29 | 035 | 0x1D | 00011101 | GS |  | Group Separator |
| 30 | 036 | 0x1E | 00011110 | RS |  | Record Separator |
| 31 | 037 | 0x1F | 00011111 | US |  | Unit Separator |
| 127 | 177 | 0x7F | 01111111 | DEL |  | Delete |