Delete character
The delete control character is the last character in the ASCII repertoire, with the code 127. It is supposed to do nothing and was designed to erase incorrect characters on paper tape. It is denoted as in caret notation and is in Unicode.
Terminal emulators may produce DEL when key or or are typed.
History
This code was originally used to mark deleted characters on punched tape, since any character could be changed to all 1s by punching holes everywhere. If a character was punched erroneously, punching out all seven bits caused this position to be ignored or deleted. In hexadecimal, this is 7F to rub out 7 bits. This character could also be used as padding to slow down printing after newlines, though the all-zero NUL was more often used.The Teletype Model 33 provided a key labelled to punch this character, and did not provide a key that produced the backspace character. Therefore, a number of less expensive computer systems that used Teletypes used this key to ignore the previous mis-typed character. Video terminals designed to replace the teletype then had to place a key that produced this code where backspace would be expected, in particular in products from Digital Equipment Corporation. On VT100 compatible terminals, this is the character generated by the key labeled. On later terminals, such as the VT510, the key is labeled and by default sent DEL, but could be set up to send BS.
Other terminals designed for systems that did not have a history of using Teletypes would usually make a key at this position send BS, leading to much confusion. Unix, in particular, had a problem in that it could only be programmed to erase the previous character for one of these, thus requiring the user to reconfigure the terminal driver for each brand of terminal. Depending on the type of terminal the designer used, software would sometimes make the shortcuts or do something, even though these sent the same code as BS and DEL, assuming the backspace key was sending the other code.
A key marked that sends BS is by far the most common on modern terminals and emulators. To ensure text is not deleted backwards, the key marked "Delete" on many terminals does not send DEL and instead sends an escape sequence such as
^3~.Current use
Unix-like operating systems can still use it as the [stty|] character, i.e., to delete the previous character in the line mode. The terminal driver still cannot be programmed to take both this and backspace: one must be chosen. However, most modern programs bypass this and use libraries such as Readline which accepts both codes. Most Unix terminal emulators can be configured to send either delete or backspace when the backspace key is pressed.DOS/Windows never used this character in any way. The BIOS keyboard driver produced backspace when the backspace key was typed and NUL with scan code 0x53 when the delete key was typed. In Windows, the delete key maps to VK_DELETE. EGA/VGA fonts, as fonts used by Win32 console, usually have the "house" symbol ⌂ at 127 code point. However, its legacy can be seen in parts of the Windows operating system: as an example, in Notepad and File Explorer used to insert the delete character until it was changed in version 1809 to make it delete the previous word, as it does in most modern applications.