- 0 (null, NUL, \0, ^@), originally intended to be an ignored character, but now used by many programming languages including C to mark the end of a string.
- 7 (bell, BEL, \a, ^G), which may cause the device to emit a warning such as a bell or beep sound or the screen flashing.
- 8 (backspace, BS, \b, ^H), may overprint the previous character.
- 9 (horizontal tab, HT, \t, ^I), moves the printing position right to the next tab stop.
- 10 (line feed, LF, \n, ^J), moves the print head down one line, or to the left edge and down. Used as the end of line marker in most UNIX systems and variants.
- 11 (vertical tab, VT, \v, ^K), vertical tabulation.
- 12 (form feed, FF, \f, ^L), to cause a printer to eject paper to the top of the next page, or a video terminal to clear the screen.
- 13 (carriage return, CR, \r, ^M), moves the printing position to the start of the line, allowing overprinting. Used as the end of line marker in Classic Mac OS, OS-9, FLEX (and variants). A CR+LF pair is used by CP/M-80 and its derivatives including DOS and Windows, and by Application Layer protocols such as FTP, SMTP, and HTTP.
- 26 (Control-Z, SUB, EOF, ^Z). Acts as an end-of-file for the Windows text-mode file i/o.
- 27 (escape, ESC, \e (GCC only), ^[). Introduces an escape sequence.