Carriage return

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Originally, carriage return was the term for the control character in Baudot code on a teletypewriter for end of line return to beginning of line and did not include line feed. Later it was used for a mechanism or lever on a typewriter that would cause the cylinder on which the paper was held (the carriage) to return to the left side of the paper after a line of text had been typed, and would usually move the paper to the next line as well. The first power carriage return was added to electric typewriters by Smith Corona in 1960. The key for this was usually labelled "carriage return" or "return". To improve the keyboard for non-English-speakers, the symbol ↵ was introduced to mark this key, since this graphic could communicate the action of the key without using words.

Computer analogues

In computing, the carriage return (CR) is one of the control characters in ASCII code, Unicode or EBCDIC that commands a printer or other sort of display to move the position of the cursor to the first position on the same line. It was mostly used along with line feed, a move to the next line, while carriage return precedes line feed to indicate a new line. The term derives from the above usage, as early printers often closely resembled typewriters; this control character would activate a physical carriage-return mechanism.

On printers, teletypes, and computer terminals that were not capable of displaying graphics, the carriage return was used without moving to the next line to allow characters to be placed on top of existing characters to produce character graphics, underlines, and crossed out text.

Many computer programs use the carriage return character, alone or with a line feed, to signal the end of a line of text, but other characters are also used for this function (see newline); others use it only for a paragraph break (a hard return). Some standards which introduce their own representations for line and paragraph control (for example HTML) treat carriage return and line feed as whitespace.

In ASCII and Unicode, the character code decimal 13 (or hexadecimal 0D) is defined to be carriage return. In the C programming language and many other languages influenced by it, \r denotes this character^[1].

User interface functionality

On Windows, Macintosh and most other GUI operating systems, hitting the return key also results in the default option of a dialog box (usually OK or Yes) being selected.

Mac OS provides differentiation between the 'return' key and 'enter' key, while Microsoft Windows does not. Though used interchangeably today, the Return key and Enter key on PC keyboards actually send different scan codes, and so can be programmed for different uses.

Summary

• Keys commonly generating the character "carriage return":

  "Enter" key

  "Return" key

  ↵ key

  Control-M

• ASCII and Unicode representation of "carriage return":

  Decimal code: 13

  Hexadecimal code: 0D

  Symbol: CR

• Programming escape codes and functions for generating a "carriage return":

  PHP, Python, Bash, C/C++, C#, Java, Javascript, Perl, Ruby: \r

  Visual Basic (VB), VBA and VB.NET: vbCr or Chr$(13)

  CFML: Chr(13)

  XML (HTML, XSLT): 

• Microsoft Office "carriage return":

  Word: Shift-Enter

  "Find & Replace" regular expression: ^p

  "Find & Replace" alternative expression: ^013

  "Find & Replace" expression for a "manual return": ^l

  Excel: Alt-Enter (Win) Cmd-Opt-Enter (OSX)

• OpenOffice.org "carriage return":

  Writer in "Find & Replace" regular expression: $

References

1. ^ Eric S. Roberts. The Art And Science of C. Addison-Wesley 1995. p311.

See also

• Enter key
• Newline
• Soft return
• Hard return

IBM/Windows keyboard (US layout) v • d • e
Esc		F1	F2	F3	F4		F5	F6	F7	F8		F9	F10	F11	F12		PrtSc/ SysRq	ScrLk	Pause/ Break
																	Ins	Home	PgUp		NumLk	/	*	-
																	Del	End	PgDn		7	8	9	+
																					4	5	6
																		↑			1	2	3	Ent
																	←	↓	→		0		.