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Tab key on a standard Windows keyboard
Tab key on a standard Windows keyboard

Tab key (abbreviation of tabulator key) on a keyboard is used to advance the cursor to the next tab stop. Microsoft Windows is a series of Software Operating systems and Graphical user interfaces produced by Microsoft. In Computing, a keyboard is an Input device partially modelled after the typewriter keyboard which uses an arrangement of buttons or keys Alphanumeric keyboards include Typewriters and Computer keyboards. A tab stop on a Typewriter is a location where the carriage movement is halted by mechanical gears

Contents

Origin

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. A typewriter is a mechanical or Electromechanical device with a set of "keys" that when pressed cause characters to be printed on a medium The space bar, spacebar, or space key, is a key on an Alphanumeric keyboard in the form of a horizontal bar in the lowermost row significantly wider 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. English 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. American Standard Code for Information Interchange ( ASCII) The most known and common tab is a horizontal tab, which in ASCII has the decimal character code of 9. A vertical tab also exists and has ASCII decimal character code 11. The EBCDIC code for HT is 5. Extended Binary Coded Decimal Interchange Code ( EBCDIC) is an 8- Bit Character encoding ( Code page) used on IBM mainframe Operating 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.

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 and 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, half 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. Fortran (previously FORTRAN) is a general-purpose, procedural, imperative Programming language that is especially suited to 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 Horizontal Tabulation Set, 137 Horizontal Tabulation with Justification and 138 Vertical Tabulation Set. 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 Process management, the White Space as described by Geary A In word processor applications, the tab key typically moves the cursor to the next tab stop. A tab stop on a Typewriter is a location where the carriage movement is halted by mechanical gears In most other graphical applications, the tab key will shift the focus to the next control or widget. In computer programming a widget (or control) is an element of a Graphical user interface (GUI that displays an information arrangement changeable by the user

A UNIX program, expand expands a tab to a number of spaces and unexpand does the opposite. Unix (officially trademarked as UNIX, sometimes also written as Unix with Small caps) is a computer

Text divided into fields delimited by tabs can be pasted into a word processor and formatted into a table with a single command.

Tabs in HTML

HTML represents the horizontal tab as but as with all whitespace characters this does not allow actual insertion of tabs into the page except inside <pre></pre> tags. HTML, an initialism of HyperText Markup Language, is the predominant Markup language for Web pages It provides a means to describe the structure

Here is an example showing the use of with <pre></pre> tags. If you write in HTML:

<pre>These 2 lines are tabbed:2005 &#09; This line uses a tab space. &#09; This line also uses a tab space. This line does not 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 does not use a Tab space.

The vertical tab is � but is not allowed in SGML, including HTML and XML 1. The Standard Generalized Markup Language ( ISO 88791986 SGML) is an ISO Standard Metalanguage in which one can define Markup languages Don't change "Extensible" 0.

The issue is of concern in the use of CSS, which asserts that in an element where white space is to be preserved:

. In Process management, the White Space as described by Geary A . . 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. English An indentation can mean two things To make notches in something or form deep recesses in a coastline for instance 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. Programmers who favor wide tabs often point out that deeply indented code is a bad thing in itself. [1][2]

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. Most programmer's 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 if their editor's tabstop width is set differently.

One early benefit of tabs, ie: compression 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.

Linus Torvalds has remarked that "Tabs are 8 characters, and thus indentations are also 8 characters. Linus Benedict Torvalds ( ˈtuːrvalds born December 28 1969 in Helsinki, Finland) is a Finnish software engineer 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. "[3]

References

  1. ^ Arrow Anti Pattern
  2. ^ Coding Horror: Flattening Arrow Code
  3. ^ Documentation/CodingStyle of Linux

External links

IBM/Windows keyboard (US layout)
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EscF1F2F3F4F5F6F7F8F9F10F11F12PrtScScrLkPause
TildeExclamation markAt signNumber signDollar signPercent signCaretAmpersandAsteriskBracketBracketUnderscorePlus and minus signsBackspaceGrave accent1 (number)2 (number)3 (number)4 (number)5 (number)6 (number)7 (number)8 (number)9 (number)0 (number)HyphenEquals signBackspaceTab keyQWERTYUIOPBracketBracketVertical barTab keyQWERTYUIOPBracketBracketBackslashCaps lockASDFGHJKLColon (punctuation)Quotation markEnter keyCaps lockASDFGHJKLSemicolonApostropheEnter keyShift keyZXCVBNMBracketBracketQuestion markShift keyShift keyZXCVBNMComma (punctuation)Full stopSlash (punctuation)Shift keyControl keyWindows keyAlt keySpace barAltGr keyWindows keyMenu keyControl key
InsHomePgUpNumLk/*-
DelEndPgDn789+
456
↑123Ent
←↓→0.
Linux (commonly pronounced ˈlɪnəks International Business Machines Corporation abbreviated IBM and nicknamed "Big Blue", is a multinational Computer Technology Microsoft Windows is a series of Software Operating systems and Graphical user interfaces produced by Microsoft. 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The Page Up and Page Down keys are two keys commonly found on Computer keyboards The two keys are primarily used to scroll up or down in documents but the scrolling In mathematics Seven is the fourth Prime number. It is not only a Mersenne prime (since 23 &minus 1 = 7 but also a In mathematics 8 is a Composite number, its Proper divisors being 1, 2, and 4. In mathematics Nine is a Composite number, its proper Divisors being 1 and 3. The plus and minus signs ( + and &minus) are Mathematical symbols used to represent the notions of positive and negative as well as the operations In mathematics Four is the smallest Composite number, its proper Divisors being and. This article discusses the number five. For the year 5 AD see 5. In mathematics Six is the second smallest Composite number, its proper Divisors being 1, 2 and 3. Cursor movement keys or arrow keys are buttons on a Computer keyboard that are either programmed or designated to move the cursor in a specified direction Mathematics For any number x: x ·1 = 1· x = x (1 is the multiplicative identity In mathematics Two has many properties in Mathematics. An Integer is called Even if it is divisible by 2 ---- In mathematics Three is the first odd Prime number, and the second smallest prime In Computer keyboards the enter key (or the return key) in most cases causes a command line, window form or Dialog box to operate Cursor movement keys or arrow keys are buttons on a Computer keyboard that are either programmed or designated to move the cursor in a specified direction Cursor movement keys or arrow keys are buttons on a Computer keyboard that are either programmed or designated to move the cursor in a specified direction Cursor movement keys or arrow keys are buttons on a Computer keyboard that are either programmed or designated to move the cursor in a specified direction In a positional Numeral system, the decimal separator is a Symbol used to mark the boundary between the integral and the fractional
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