The deletecontrol character (also called DEL or rubout) is the last character in the ASCII repertoire, with the code 127.[1] 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 U+007F in Unicode.
Terminal emulators may produce DEL when ← Backspace key or Control+← Backspace or Control+? are typed.
"Delete" along with some other ASCII control characters and space as they appear on punched tape
This code was originally used to mark deleted characters on punched tape, since any character could be changed to all ones by punching holes everywhere. If a character was punched erroneously, punching out all seven bits caused this position to be ignored or deleted.[2][3] In hexadecimal, this is 7F to rub out 7 bits (FF to rubout 8 bits was used for 8-bit codes). 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 RUB OUT to punch this character (after the user backed up the tape using another button), and did not provide a key that produced the Backspace character (BS). Therefore, a number of less-expensive computer systems that used Teletypes used this key (and thus the Delete code) 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 Delete.[4][5] On later terminals, such as the VT510, the key is labeled ⌫ (called backarrow in the manual[6]) 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 an annoying problem in that it could only be programmed to erase the previous character for one of these (not both), 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 Ctrl+H or Ctrl+? 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 Backspace ← that sends BS is by far the most common on modern terminals and emulators. To make sure they don't delete backwards, the key marked "Delete" on many terminals does not send DEL and instead sends an escape sequence such as ^[[3~.[7]
Current use
Unix-like operating systems can still use it as the erase 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.[8] In Windows the delete key maps to VK_DELETE (0x2E).[9]EGA/VGA fonts, as fonts used by Win32 console, usually have the "house" symbol ⌂ at 127 (0x7F) code point, see Code page 437 for details. However, its legacy can be seen in parts of the Windows operating system: as an example, Control+← Backspace in Microsoft Notepad used to insert the delete character[10] until it was changed in 2018 to make it delete the previous word.[11]
^"The New and Improved Windows 10 Notepad: Useful Tips and Features". 23 November 2018.
June 15, 2023
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The delete control character also called DEL or rubout is the last character in the ASCII repertoire with the code 127 1 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 U 007F in Unicode Terminal emulators may produce DEL when Backspace key or Control Backspace or Control are typed Contents 1 History 2 Current use 3 See also 4 ReferencesHistory Edit NUL CR LF DEL SP Delete along with some other ASCII control characters and space as they appear on punched tapeThis code was originally used to mark deleted characters on punched tape since any character could be changed to all ones by punching holes everywhere If a character was punched erroneously punching out all seven bits caused this position to be ignored or deleted 2 3 In hexadecimal this is 7F to rub out 7 bits FF to rubout 8 bits was used for 8 bit codes 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 RUB OUT to punch this character after the user backed up the tape using another button and did not provide a key that produced the Backspace character BS Therefore a number of less expensive computer systems that used Teletypes used this key and thus the Delete code 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 Delete 4 5 On later terminals such as the VT510 the key is labeled called backarrow in the manual 6 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 an annoying problem in that it could only be programmed to erase the previous character for one of these not both 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 Ctrl H or Ctrl 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 Backspace that sends BS is by far the most common on modern terminals and emulators To make sure they don t delete backwards the key marked Delete on many terminals does not send DEL and instead sends an escape sequence such as 3 7 Current use EditUnix like operating systems can still use it as the erase 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 8 In Windows the delete key maps to VK DELETE 0x2E 9 EGA VGA fonts as fonts used by Win32 console usually have the house symbol at 127 0x7F code point see Code page 437 for details However its legacy can be seen in parts of the Windows operating system as an example Control Backspace in Microsoft Notepad used to insert the delete character 10 until it was changed in 2018 to make it delete the previous word 11 See also EditEight Ones BackspaceReferences Edit Vint Cerf October 16 1969 ASCII format for Network Interchange IETF doi 10 17487 RFC0020 RFC 20 Robert C Martin 2011 The Clean Coder A Code of Conduct for Professional Programmers Pearson Education ISBN 9780132542883 LaFarr 18 August 2006 Paper Tape First Machinable I O VT100 Family of Video Terminals vt100 net VT100 User Guide Chapter 3 Table 3 4 Function Key Codes vt100 net Archived from the original on 2016 03 14 Retrieved 2015 04 12 VT510 Video Terminal Programmer Information Chapter 5 ANSI Control Functions vt100 net VT510 Video Terminal Programmer Information Chapter 8 Keyboard Processing vt100 net Archived from the original on 2016 03 04 Retrieved 2015 04 12 Keyboard scan code Character code combinations PC DOS Retro Virtual Key Codes Winuser h Win32 apps Shortcuts Notepad CTRL Backspace behavior The New and Improved Windows 10 Notepad Useful Tips and Features 23 November 2018 Retrieved from https en wikipedia org w index php title Delete character amp oldid 1157566625, wikipedia, wiki, book, books, library,
