The ISO/IEC 2022 system of specifying control and graphic characters allows other C0 and C1 sets to be available for specialized applications, but they are rarely used.
Only a few codes have maintained their use: BEL, ESC, and the format effector[1] (FEn) characters BS, TAB, LF, VT, FF, and CR.
Some data transfer protocols such as ANPA-1312, Kermit, and XMODEM do make extensive use of SOH, STX, ETX, EOT, ACK, NAK and SYN for purposes approximating their original definitions; and some file formats use the "Information Separators" (ISn) such as the Unix info format[2] and Python's splitlines string method.
[26] Symbolic names defined by RFC 1345 and early drafts of ISO 10646, but not in ISO/IEC 6429 (PAD, HOP and SGC) are also used.
Nowadays if these codes are encountered it is far more likely they are intended to be printing characters from that position of Windows-1252 or Mac OS Roman.
Some terminal emulators, including xterm, use OSC sequences for setting the window title and changing the colour palette.
@ and the above C1 set chosen with the sequence ESC " C.[24] Several official and unofficial alternatives have been defined, but this is pretty much obsolete.
[55] The rest of the codes are transparent to Unicode and their meanings are left to higher-level protocols, with ISO/IEC 6429 suggested as a default.