 The tab key on a standard Windows keyboard (top left of picture) The tab key on a keyboard is used to advance the cursor to the next "tab stop". ImageMetadata File history File links Keyboard-left_keys. ...
ImageMetadata File history File links Keyboard-left_keys. ...
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A tabstop on a typewriter is a location where the carriage movement is halted by mechanical gears. ...
Origin Tab is the abbreviation of Tabulator. To tabulate (tabulating) means putting something into a table or chart.
When a typist wanted to type a table, there was a lot of time-consuming and repetitive use of the space bar and backspace key. To simplify this, a bar was placed in the mechanism with a moveable lever for every position across the page. Initially these were set by hand, but later a "tab set" and "tab clear" keys were added. When the tab key was depressed the carriage advanced to the next "tab stop". These were set to correspond to the particular column locations of the table (hence "tab") being worked on. The tab mechanism also came into its own as a rapid and consistent way of uniformly indenting the first line of each paragraph. Mechanical desktop typewriters, such as this Underwood Five, were long time standards of government agencies, newsrooms, and sales offices. ...
A computer keyboard Space bar is a key on an alphanumeric keyboard in the form of a horizontal bar in the lowermost row, significantly wider than other keys. ...
An indentation can mean two things: To make notches in something or form deep recesses in a coastline for instance. ...
ASCII and EBCDIC Several tab characters are included as ASCII control characters, used for text alignment. The most known and common tab is a horizontal tab (HT), which in ASCII has the decimal character code of 9. A vertical tab (VT) also exists and has ASCII decimal character code 11. (The EBCDIC code for HT is 5. The VT is 11, or hex 0B, the same as ASCII.) The horizontal tab is usually generated by the tab key on a standard keyboard. Image:ASCII fullsvg There are 95 printable ASCII characters, numbered 32 to 126. ...
EBCDIC (Extended Binary Coded Decimal Interchange Code) is an 8-bit character encoding (code page) used on IBM mainframe operating systems, like z/OS, OS/390, VM and VSE, as well as IBM minicomputer operating systems like OS/400 and i5/OS. It is also employed on various non-IBM...
Originally printers used mechanical tab stops to indicate where the tabs went. This was done horizontally with movable metal prongs in a row, and vertically with a loop of mylar or other tape the length of a page with holes punched in it to indicate the tab stops. Initially these were manually set to match the preprinted forms the printer was going to print. The intention was to have the machine be programmed with other control characters to set/clear the stops, but it is unclear if any popular printers implemented this. Instead it was rather quickly replaced with fixed tab stops, at every multiple of 8 characters horizontally and every 6 lines vertically, so they simply became a form of data compression, since a printing program could easily add the necessary spaces to move to any position wanted on a form. The vertical size was chosen to be 1 inch. It is unclear why the 8-character horizontal size was chosen, as 5 characters (1/2 inch in a typical printer at that time) was much more popular at that time as a paragraph indentation. It may have been chosen to match early Fortran conventions for where the statement text started after the line number and continuation character. Or it may have been chosen as the smallest size that would fit numbers typically printed in a table.
ISO 8859 also includes the codes 136 HTS Horizontal Tabulation Set, 137 HTJ Horizontal Tabulation with Justification and 138 VTS Vertical Tabulation Set. ISO 8859, more formally ISO/IEC 8859, is a joint ISO and IEC standard for 8-bit character encodings for use by computers. ...
Tabs are almost always rendered as a form of whitespace larger than a single space, while some text editors mark tabs with special graphics to facilitate distinguishing tabs and whitespaces. In word processor applications, the tab key typically moves the cursor to the next tab stop. In most other graphical applications, the tab key will shift the focus to the next control or widget. For information on the programming language Whitespace, see Whitespace programming language. ...
A tabstop on a typewriter is a location where the carriage movement is halted by mechanical gears. ...
Various widgets. ...
A UNIX program, expand expands a tab to a number of spaces and unexpand does the opposite.
Text divided into fields delimited by tabs can be pasted into a word processor and formatted into a table with a single command. A word processor (also more formally known as a document preparation system) is a computer application used for the production (including composition, editing, formatting, and possibly printing) of any sort of viewable or printed material. ...
Tabs in HTML HTML represents the horizontal tab as 	 but as with all whitespace characters this doesn't allow actual insertion of tabs into the page except inside <pre> tags. HTML, an initialism of Hypertext Markup Language, is the predominant markup language for web pages. ...
Here is an example showing the use of 	 with <pre> tags. If you write in HTML:
<pre> These 2 lines are tabbed: 2005 	 This line uses a Tab space. 	 This line also uses a Tab space. This line doesn't use a Tab space. </pre> the result would be something like this: These 2 lines are tabbed: 2005 This line uses a Tab space. This line also uses a Tab space. This line doesn't use a Tab space. The vertical tab is  but is not allowed in SGML (including HTML) or XML 1.0. The Standard Generalized Markup Language (SGML) is a metalanguage in which one can define markup languages for documents. ...
The Extensible Markup Language (XML) is a general-purpose markup language. ...
The issue is of concern in the use of Cascading Style Sheets, which asserts that in an element where white space is to be preserved: In web development, Cascading Style Sheets (CSS) is a stylesheet language used to describe the presentation of a document written in a markup language. ...
Look up white space, whitespace in Wiktionary, the free dictionary. ...
... 2. All tabs (U+0009) are rendered as a horizontal shift that lines up the start edge of the next glyph with the next tab stop. Tab stops occur at points that are mutiples of 8 times the width of a space (U+0020) rendered in the block's font from the block's starting content edge.
Tabs in programming In computer programming, the use of tabs for code formatting and indentation is an ongoing debate. The vast majority of code is written as plain ASCII, lacking the extra formatting information more elaborate markups and proprietary file formats provide. Some programmers consider the use of 8 spaces per tab to be excessive, such as when viewing very deeply nested (and therefore very deeply indented) lines of code. Others then point out that deeply indented code is to be considered a bad thing in itself. This of course is wrong; good programming practice means indenting the code to the extent necessary - no more, no less. Programming redirects here. ...
An indentation can mean two things: To make notches in something or form deep recesses in a coastline for instance. ...
Programmer's editors usually default to having the TAB key generate hard tabs, that is actual HT characters, but some editors expand them to space (SP) characters instead, often referred to as soft tabs. Good editors can be configured to perform either.
There are many arguments for and against using hard tabs in code. The most incompatibility and conversion issues ensue when the tab key generates HT characters and the editor is configured for tab stops spaced anything but the de-facto standard, which for Unix, Unix-derived systems and older systems is every 8 characters, and for Windows programming, every 4 characters. Interesting possibilities include 2 and even 3. When deviating from the system's de facto standard, then inevitably some lines will be formatted with spaces, others with tabs, or even both. As soon as the code ends up on someone else's screen it will look different and usually jumbled and untidy.
One early benefit of tabs, i.e. compression (see above), is now considered less relevant as desktop storage has become cheaper, and sophisticated compression algorithms can provide much greater benefits, albeit at the cost of greater complexity. Source coding redirects here. ...
Tabs in terminals In many terminals pressing the tab key results in tab completion, or auto-completion of the command line. A computer terminal is an electronic or electromechanical hardware device that is used for entering data into, and displaying data from, a computer or a computing system. ...
Tab completion is a function of many command line interfaces, especially Unix shells, that allows portions of an incomplete filename or commands to be filled in when the Tab key is pressed. ...
In some IRC programs, tab finishes a username.
Notable advocates
In favour
Against - Linus Torvalds: Tabs are 8 characters, and thus indentations are also 8 characters. There are heretic movements that try to make indentations 4 (or even 2!) characters deep, and that is akin to trying to define the value of PI to be 3. (From Documentation/CodingStyle of Linux)
Linus Benedict Torvalds ; born December 28, 1969 in Helsinki, Finland, is a Finnish software engineer best known for initiating the development of the Linux kernel. ...
This article is about operating systems that use the Linux kernel. ...
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