The Delete character is a control character in the American Standard Code for Information Interchange (ASCII) and Unicode character sets, designated by the code point 127 (decimal) or 0x7F (hexadecimal). It is represented in Unicode as U+007F DELETE.
Historical background
The Delete character was introduced with the original 1963 ASCII standard. Its primary purpose was to provide a mechanism for correcting errors on paper tape and later on magnetic tape. On paper tape, a punched hole representing a character could be physically removed by punching all seven bits (i.e., setting them to the "all‑ones" pattern), which corresponded to the 0x7F pattern; this action would render the original character unreadable, effectively deleting it. The same principle was applied to early computer storage media and later to software editing contexts.
Functional usage
In contemporary computing, the Delete character functions as a non‑printing control code that signals the removal of a preceding character or a selected range of characters, depending on the software environment. Typical uses include:
- Text editing: Pressing the Delete key on a keyboard (often labeled “Del”) sends the Delete character to a text editor, which interprets it as a command to erase the character to the right of the cursor (or the selected text).
- Terminal emulation: In command‑line interfaces, the Delete character can be part of escape sequences that control cursor movement or screen updating.
- Data transmission: In serial communication protocols, the Delete character may be employed as a signal for back‑spacing or error correction, though more modern protocols frequently use other control codes (e.g., BS – Backspace, 0x08).
Representation in Unicode and other character sets
In the Unicode Standard, the Delete character retains its original code point U+007F and belongs to the C0 Controls and Basic Latin block. It is also present in other character encoding standards derived from ASCII, such as ISO/IEC 646 and UTF‑8 (where it is encoded as the single byte 0x7F).
Keyboard association
The Delete key on modern computer keyboards is a hardware key that typically generates the Delete character (ASCII 127) when pressed, though the exact scan code can vary among keyboard layouts and operating systems. On many systems, a separate Backspace key generates the BS control character (ASCII 8), which deletes the character to the left of the cursor.
Cultural and technical significance
The Delete character is part of the original set of 33 control characters defined by ASCII, reflecting early design considerations for error handling in mechanical data storage. Its continued presence in modern character sets underscores the legacy influence of early computing conventions on current software and hardware interfaces.
References
- American National Standards Institute, ASCII – American Standard Code for Information Interchange, ANSI X3.4‑1968.
- The Unicode Standard, Version 15.0, Unicode Consortium, 2022.
- John R. Levine, Unicode and the Widespread Adoption of the Delete Character, Communications of the ACM, vol. 49, no. 4, 2006.