Backspace (← Backspace, ⌫) is the keyboard key that in typewriters originally pushed the carriage one position backwards, and in modern computer systems typically moves the display cursor one position backwards, [note 1] deletes the character at that position, and shifts back any text after [note 2] that position by one character.
![An early typewriter with a backspacer[sic] key. (Blickensderfer Model 7) Blickensderfer model 7, 1909.jpg](http://upload.wikimedia.org/wikipedia/commons/thumb/0/0f/Blickensderfer_model_7%2C_1909.jpg/220px-Blickensderfer_model_7%2C_1909.jpg)
Although the term "backspace" is the traditional name of the key which steps the carriage back and/or [note 3] deletes the previous character, typically to the left of the cursor, the actual key may be labeled in a variety of ways, for example delete, [1] erase, [note 4] or with a left pointing arrow. [3] A dedicated symbol for "backspace" exists as U+232B ⌫ but its use as a keyboard label is not universal. Some very early typewriters labeled this key the backspacer key.
Backspace is distinct from the delete key, which in a teletypewriter would punch out all the holes in punched paper tape to strike out a character, and in modern computers deletes text at or following the cursor position. Also, the delete key often works as a generic command to remove an object (such as an image inside a document, or a file in a file manager), while backspace usually does not. [4] [5] Full-size Mac keyboards have two keys labeled delete; a key that functions as a backspace key, and a key that functions as a delete key. Smaller Mac keyboards, such as laptop keyboards, have only a key that functions as a backspace key. [6]
In some [note 5] typewriters, a typist would, for example, type a lowercase letter A with acute accent (á) by typing a lowercase letter A, backspace, and then the acute accent key. This technique (also known as overstrike) is the basis for such spacing modifiers in computer character sets such as the ASCII caret (^, for the circumflex accent). Backspace composition no longer works with typical modern digital displays or typesetting systems. [note 6] It has to some degree been replaced with the combining diacritical marks mechanism of Unicode, though such characters do not work well with many fonts, and precomposed characters continue to be used. Some software like TeX or Microsoft Windows use the opposite method for diacritical marks, namely positioning the accent first, and then the base letter on its position.
In modern systems, the backspace key is often mapped to the delete character (0x7f in ASCII or Unicode), although the backspace key's function of deleting the character before the cursor remains. [3] In computers, backspace can also delete a preceding newline character, something generally inapplicable to typewriters.
The backspace key is commonly used to go back a page or up one level in graphical web or file browsers.
Pressing the backspace key on a computer terminal would generate the ASCII code 08, BS or Backspace, a control code which would delete the preceding character. That control code could also be accessed by pressing ( Control +H, as H is the eighth letter of the Latin alphabet. Terminals which did not have the backspace code mapped to the function of moving the cursor backwards and deleting the preceding character would display the symbols ^H (caret, H) when the backspace key was pressed. Even if a terminal did interpret backspace by deleting the preceding character, the system receiving the text might not. Then, the sender's screen would show a message without the supposedly deleted text, while that text, and the deletion codes, would be visible to the recipient. This sequence is still used humorously for epanorthosis by computer literates, denoting the deletion of a pretended blunder, much like a strikethrough; in this case, however, the ^H symbol is faked by typing a regular '^' followed by typing a regular 'H'.
Example:
An alternative sometimes seen is ^W, which is the shortcut to delete the previous word in the Berkeley Unix terminal line discipline. This shortcut has also made it into the insert mode of the Vi text editor and its clone Vim. [8]
^U deletes a line. [9]
In a mainframe environment, to backspace means to move a magnetic tape backwards, typically to the previous block.
| Esc | F1 | F2 | F3 | F4 | F5 | F6 | F7 | F8 | F9 | F10 | F11 | F12 | PrtScn/ SysRq | Scroll Lock | Pause/ Break | |||||||||
 | Insert | Home | PgUp | Num Lock | ∕ | ∗ | − | |||||||||||||||||
| Delete | End | PgDn | 7 | 8 | 9 | + | ||||||||||||||||||
| 4 | 5 | 6 | ||||||||||||||||||||||
| ↑ | 1 | 2 | 3 | Enter | ||||||||||||||||||||
| ← | ↓ | → | 0 Ins | . Del | ||||||||||||||||||||
ASCII, an acronym for American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. ASCII has just 128 code points, of which only 95 are printable characters, which severely limit its scope. The set of available punctuation had significant impact on the syntax of computer languages and text markup. ASCII hugely influenced the design of character sets used by modern computers, including Unicode which has over a million code points, but the first 128 of these are the same as ASCII.
ASCII art is a graphic design technique that uses computers for presentation and consists of pictures pieced together from the 95 printable characters defined by the ASCII Standard from 1963 and ASCII compliant character sets with proprietary extended characters. The term is also loosely used to refer to text-based visual art in general. ASCII art can be created with any text editor, and is often used with free-form languages. Most examples of ASCII art require a fixed-width font such as Courier for presentation.
In computing and telecommunications, a control character or non-printing character (NPC) is a code point in a character set that does not represent a written character or symbol. They are used as in-band signaling to cause effects other than the addition of a symbol to the text. All other characters are mainly graphic characters, also known as printing characters, except perhaps for "space" characters. In the ASCII standard there are 33 control characters, such as code 7, BEL, which rings a terminal bell.
The keyboard for IBM PC-compatible computers is standardized. However, during the more than 30 years of PC architecture being frequently updated, many keyboard layout variations have been developed.
QWERTY is a keyboard layout for Latin-script alphabets. The name comes from the order of the first six keys on the top letter row of the keyboard: QWERTY. The QWERTY design is based on a layout included in the Sholes and Glidden typewriter sold via E. Remington and Sons from 1874. QWERTY became popular with the success of the Remington No. 2 of 1878 and remains in ubiquitous use.
In computing, a Control keyCtrl is a modifier key which, when pressed in conjunction with another key, performs a special operation. Similarly to the Shift key, the Control key rarely performs any function when pressed by itself. The Control key is located on or near the bottom left side of most keyboards, with many featuring an additional one at the bottom right.
The tab keyTab ↹ on a keyboard is used to advance the cursor to the next tab stop.
A text box also called an input box, text field or text entry box, is a control element of a graphical user interface, that should enable the user to input text information to be used by a program. Human Interface Guidelines recommend a single-line text box when only one line of input is required, and a multi-line text box only if more than one line of input may be required. Non-editable text boxes can serve the purpose of simply displaying text.
A dead key is a special kind of modifier key on a mechanical typewriter, or computer keyboard, that is typically used to attach a specific diacritic to a base letter. The dead key does not generate a (complete) character by itself, but modifies the character generated by the key struck immediately after. Thus, a dedicated key is not needed for each possible combination of a diacritic and a letter, but rather only one dead key for each diacritic is needed, in addition to the normal base letter keys.
The backtick` is a typographical mark used mainly in computing. It is also known as backquote, grave, or grave accent.
The Alt keyAlt on a computer keyboard is used to change (alternate) the function of other pressed keys. Thus, the Alt key is a modifier key, used in a similar fashion to the Shift key. For example, simply pressing A will type the letter 'a', but holding down the Alt key while pressing A will cause the computer to perform an Alt+A function, which varies from program to program. The international standard ISO/IEC 9995-2 calls it Alternate key. The key is located on either side of the space bar, but in non-US PC keyboard layouts, rather than a second Alt key, there is an 'Alt Gr' key to the right of the space bar. Both placements are in accordance with ISO/IEC 9995-2. With some keyboard mappings, the right Alt key can be reconfigured to function as an AltGr key although not engraved as such.
In typography, overstrike is a method of printing characters that are missing from the printer's character set. The character is created by placing one character on another one – for example, overstriking ⟨L⟩ with ⟨-⟩ results in printing a ⟨Ł⟩ character.
Caret notation is a notation for control characters in ASCII. The notation assigns ^A to control-code 1, sequentially through the alphabet to ^Z assigned to control-code 26 (0x1A). For the control-codes outside of the range 1–26, the notation extends to the adjacent, non-alphabetic ASCII characters.
The Insert keyInsert is a key commonly found on computer keyboards.
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 U+007F in Unicode.
A computer keyboard is a peripheral input device modeled after the typewriter keyboard which uses an arrangement of buttons or keys to act as mechanical levers or electronic switches. Replacing early punched cards and paper tape technology, interaction via teleprinter-style keyboards have been the main input method for computers since the 1970s, supplemented by the computer mouse since the 1980s.
A typographic approximation is a replacement of an element of the writing system with another glyph or glyphs. The replacement may be a nearly homographic character, a digraph, or a character string. An approximation is different from a typographical error in that an approximation is intentional and aims to preserve the visual appearance of the original. The concept of approximation also applies to the World Wide Web and other forms of textual information available via digital media, though usually at the level of characters, not glyphs.
The delete key is a button on most computer keyboards which is typically used to delete either the character ahead of or beneath the cursor, or the currently-selected object. The key is sometimes referred to as the "forward delete" key. This is because the backspace key also deletes characters, but to the left of the cursor. On many keyboards, such as most Apple keyboards, the key with the backspace function is also labelled "delete".
The Hazeltine 1500 was a popular smart terminal introduced by Hazeltine Corporation in April 1977 at a price of $1,125. Using a microprocessor and semiconductor random access memory, it implemented the basic features of the earlier Hazeltine 2000 in a much smaller and less expensive system, less than half the price. It came to market just as the microcomputer revolution was taking off, and the 1500 was very popular among early hobbyist users.
Caret is the name used familiarly for the character ^ provided on most QWERTY keyboards by typing ⇧ Shift+6. The symbol has a variety of uses in programming and mathematics. The name "caret" arose from its visual similarity to the original proofreader's caret, ‸, a mark used in proofreading to indicate where a punctuation mark, word, or phrase should be inserted into a document. The ASCII standard (X3.64.1977) calls it a "circumflex"; the Unicode standard calls it a "circumflex accent", although it is no longer practicable for that purpose.
