Le code ASCII - caractères de contrôle
Au nombre de 32 (soit 25), les caractères de contrôle permettent de commander des appareils périphériques comme les écrans, les imprimantes et les modems. Certains caractères servent à positionner le curseur : backspace, tab, linefeed, carriage return, d'autres à contrôler les transmissions et d'autres encore servent à séparer les informations.
| Dec | Hex | Description ISO 646 | Description ASCII |
| 0 | $00 | NUL | Null |
| 1 | $01 | TC1 / Transmission Control character 1 | SOH Start Of Heading |
| 2 | $02 | TC2 / Transmission Control character 2 | STX Start of TeXt |
| 3 | $03 | TC3 / Transmission Control character 3 | ETX End of TeXt |
| 4 | $04 | TC4 / Transmission Control character 4 | EOT End Of Transmission |
| 5 | $05 | TC5 / Transmission Control character 5 | ENQ ENQuiry |
| 6 | $06 | TC6 / Transmission Control character 6 | ACK ACKnowledge |
| 7 | $07 | BEL / | Bell |
| 8 | $08 | FE0 Format Effector 0 | BS Back Space |
| 9 | $09 | FE1 Format Effector 1 | HT Horizontal Tab |
| 10 | $0A | FE2 Format Effector 2 | LF Line Feed |
| 11 | $0B | FE3 Format Effector 3 | VT Vertical Tab |
| 12 | $0C | FE4 Format Effector 4 | FF Form Feed |
| 13 | $0D | FE5 Format Effector 5 | CR Carriage Return |
| 14 | $0E | SO Shift Out (7-bit environment) | LS1 Locking Shift 1 |
| 15 | $0F | SI Shift In (7-bit environment | LS0 Locking Shift 0 |
| 16 | $10 | TC7 Transmission Control character 7 | DLE Data Link Escape |
| 17 | $11 | DC1 | DC1 Device Control 1 |
| 18 | $12 | DC2 | DC2 Device Control 2 |
| 19 | $13 | DC3 | DC3 Device Control 3 |
| 20 | $14 | DC4 | DC4 Device Control 4 |
| 21 | $15 | TC8 Transmission Control character 8 | NAK Negative AcKnowledgement |
| 22 | $16 | TC9 Transmission Control character 9 | SYN SYNchronous idle |
| 23 | $17 | TC10 Transmission Control character 10 | ETB End of Transmission Block |
| 24 | $18 | CAN | CANcel |
| 25 | $19 | EM | End of Medium |
| 26 | $1A | SUB | SUBstitute character |
| 27 | $1B | ESC | ESCape |
| 28 | $1C | IS4 Information Separator 4 | FS File Separator |
| 29 | $1D | IS3 Information Separator 3 | GS Group Separator |
| 30 | $1E | IS2 Information Separator 2 | RS Record Separator |
| 31 | $1F | IS1 Information Separator 1 | US Unit Separator |