Backspace key: function, history, and differences from Delete

Historical use for accents and diacritics

On older typewriters, combining a base letter with an accent was sometimes done by typing the letter, using backspace, then typing the accent so the two characters overstruck. That practice inspired some conventions in early character sets—for example the use of the caret in ASCII to represent a circumflex when no precomposed character was available. With modern systems this overstrike method has largely been superseded by Unicode combining marks (Unicode) and by precomposed characters, although font and input support for combining marks can be inconsistent. Some software systems, including typesetting tools and certain operating environments such as Microsoft Windows, instead apply diacritics by positioning the mark first and then inserting the base letter at that location.

Control codes and conventions

When used on computer terminals, pressing backspace historically produced the ASCII control code for Backspace (code 08, commonly written as BS). The same control code can be generated by the keyboard shortcut Control-H, since H is the eighth letter of the alphabet. Terminals that did not interpret the control code as movement and deletion often displayed the sequence ^H instead; programmers and chatters later adopted this as a jokey way to mark a correction in plain text.

Example of that humorous notation:

My slave-dri^H^H^H^H^H^H^H^H^Hboss decided to stall the project.

Shortcuts for larger deletions

In many Unix-style terminal line disciplines a single ^W deletes the previous word, which can replace a run of ^H characters. That behavior is available in text editors such as Vi. For erasing an entire line, ^U (kill line) is commonly used.

Backspace vs. Delete

The backspace key is not the same as the Delete key. On keyboards and in older punched-card or paper-based computer media, Delete could mark or remove the character at or after the cursor (in some systems it physically punched out positions to indicate removal). In graphical user interfaces the Delete key is often mapped to a general remove command (deleting files, images, or other objects), while backspace commonly retains its leftward-deletion role or has no effect in certain contexts.

Some environments map the backspace key to the DEL control character (0x7F) internally while keeping the visible behavior of erasing the character before the cursor.

Other uses and terminology

In legacy mainframe terminology, to backspace a tape is to move a mainframe-style magnetic tape backward, usually to the previous block. In modern graphical file explorers and when navigating the Web, pressing backspace is frequently interpreted as a command to go back to the previous folder or page in many web browsers, although this mapping varies by application and operating system.

The physical key itself is labeled in different ways across platforms and keyboards: common markings include a left-pointing arrow, the word Delete, Erase (seen on some educational laptops), or the word Backspace. The exact label does not always reflect the key's behavior in software.