What are carriage return linefeed and form feed

Question

What is the meaning of the following control characters     Carriage return Line feed Form feed

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Carriage return and line feed are also references to typewriters  in that the with a small push on the handle on the left side of the carriage  the place where the paper goes   the paper would rotate a small amount around the cylinder  advancing the document one line  If you had finished typing one line  and wanted to continue on to the next  you pushed harder  both advancing a line and sliding the carriage all the way to the right  then resuming typing left to right again as the carriage traveled with each keystroke  Needless to say  word-wrap was the default setting for all word processing of the era  P D

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Have a look at Wikipedia      Systems based on ASCII or a compatible character set use either LF  Line feed    n   0x0A  10 in decimal  or CR  Carriage return    r   0x0D  13 in decimal  individually  or CR followed by LF  CR LF  0x0D 0x0A   These characters are based on printer commands  The line feed indicated that one line of paper should feed out of the printer  and a carriage return indicated that the printer carriage should return to the beginning of the current line

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Carriage return means to return to the beginning of the current line without advancing downward   The name comes from a printer s carriage  as monitors were rare when the name was coined   This is commonly escaped as  r  abbreviated CR  and has ASCII value 13 or 0x0D   Linefeed means to advance downward to the next line  however  it has been repurposed and renamed   Used as  newline   it terminates lines  commonly confused with separating lines    This is commonly escaped as  n  abbreviated LF or NL  and has ASCII value 10 or 0x0A  CRLF  but not CRNL  is used for the pair  r n   Form feed means advance downward to the next  page    It was commonly used as page separators  but now is also used as section separators   It s uncommonly used in source code to divide logically independent functions or groups of functions    Text editors can use this character when you  insert a page break    This is commonly escaped as  f  abbreviated FF  and has ASCII value 12 or 0x0C     As control characters  they may be interpreted in various ways   The most common difference  and probably the only one worth worrying about  is lines end with CRLF on Windows  NL on Unix-likes  and CR on older Macs  the situation has changed with OS X to be like Unix    Note the shift in meaning from LF to NL  for the exact same character  gives the differences between Windows and Unix    Windows is  of course  newer than Unix  so it didn t adopt this semantic shift   I don t know the history of Macs using CR    Many text editors can read files in any of these three formats and convert between them  but not all utilities can   Form feed is a bit more interesting  even though less commonly used directly   and with the usual definition of page separator  it can only come between lines  e g  after the newline sequence of NL  CRLF  or CR  or at the start or end of the file

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As a supplement   1  Carriage return     It s a printer terminology meaning changing the print location to the beginning of current line  In computer world  it means return to the beginning of current line in most cases but stands for new line rarely   2  Line feed     It s a printer terminology meaning advancing the paper one line  So Carriage return and Line feed are used together to start to print at the beginning of a new line  In computer world  it generally has the same meaning as newline   3  Form feed    It s a printer terminology  I like the explanation in this thread       If you were programming for a 1980s-style printer  it would eject the   paper and start a new page  You are virtually certain to never need   it       http   en wikipedia org wiki Form feed   It s almost obsolete and you can refer to Escape sequence  f - form feed - what exactly is it  for detailed explanation   Note  we can use CR or LF or CRLF to stand for newline in some platforms but newline can t be stood by them in some other platforms  Refer to wiki Newline for details      LF     Multics  Unix and Unix-like systems  Linux  OS X  FreeBSD  AIX    Xenix  etc    BeOS  Amiga  RISC OS  and others      CR     Commodore 8-bit machines  Acorn BBC  ZX Spectrum  TRS-80  Apple   II family  Oberon  the classic Mac OS up to version 9  MIT Lisp   Machine and OS-9      RS     QNX pre-POSIX implementation      0x9B   Atari 8-bit machines using ATASCII variant of ASCII  155 in   decimal       CR LF  Microsoft Windows  DOS  MS-DOS  PC DOS  etc    DEC TOPS-10    RT-11  CP M  MP M  Atari TOS  OS 2  Symbian OS  Palm OS  Amstrad CPC    and most other early non-Unix and non-IBM OSes      LF CR  Acorn BBC and RISC OS spooled text output

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r is carriage return and moves the cursor back like if i will do-  printf  stackoverflow rnine   ninekoverflow   means it has shifted the cursor to the beginning of  stackoverflow  and overwrites the starting four characters since  nine  is four character long    n is new line character which changes the line and takes the cursor to the beginning of a new line like-  printf  stackoverflow nnine   stackoverflow nine    f is form feed  its use has become obsolete but it is used for giving indentation like  printf  stackoverflow fnine   stackoverflow              nine   if i will write like-  printf  stackoverflow fnine fgreat   stackoverflow              nine                  great

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On old paper-printer terminals  advancing to the next line involved two actions  moving the print head back to the beginning of the horizontal scan range  carriage return  and advancing the roll of paper being printed on  line feed    Since we no longer use paper-printer terminals  those actions aren t really relevant anymore  but the characters used to signal them have stuck around in various incarnations

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In Short    Carriage return  r or 0xD   To take control at starting of same line   Line Feed  n or 0xA   To Take control at starting of next line   form feed  f or 0xC   To take control at starting of next page

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f is used for page break  You cannot see any effect in the console  But when you use this character constant in your file then you can see the difference   Other example is that if you can redirect your output to a file then you don t have to write a file or use file handling   For ex   Write this code in c    void main             clrscr        cout lt  lt  helloooooo         cout lt  lt   f       cout lt  lt  hiiiii         and when you compile this it generate  an exe for ex  abc exe   then you can redirect your output to a file using this   abc  gt  xyz doc  then open the file xyz doc you can see the actual page break between hellooo and hiiii

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Apart from above information  there is still an interesting history of LF   n  and CR   r    Original author       Source   http   www ruanyifeng com blog 2006 04 post 213 html   Before computer came out  there was a type of teleprinter called Teletype Model 33  It can print 10 characters each second  But there is one problem with this  after finishing printing each line  it will take 0 2 second to move to next line  which is time of printing 2 characters  If a new characters is transferred during this 0 2 second  then this new character will be lost   So scientists found a way to solve this problem  they add two ending characters after each line  one is  Carriage return   which is to tell the printer to bring the print head to the left   the other one is  Line feed   it tells the printer to move the paper up 1 line   Later  computer became popular  these two concepts are used on computers  At that time  the storage device was very expensive  so some scientists said that it was expensive to add two characters at the end of each line  one is enough  so there are some arguments about which one to use   In UNIX Mac and Linux    n  is put at the end of each line  in Windows    r n  is put at the end of each line  The consequence of this use is that files in UNIX Mac will be displayed in one line if opened in Windows  While file in Windows will have one   M at the end of each line if opened in UNIX or Mac

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Those are non-printing characters  relating to the concept of  new line    n is linefeed   r is carriage return  On different platforms they have different meanings  relative to a valid new line  In windows  a new line is  r n  In linux   n  In mac   r   In practice  you put them in any string  and it will have effect on the print-out of the string

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n  is the linefeed character   It means end the present line and go to a new line for anyone who is reading it

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Consider an IBM 1403 impact printer  CR moved the print head to the start of the line  but did NOT advance the paper  This allowed for  overprinting   placing multiple lines of output on one line  Things like underlining were achieved this way  as was BOLD print  LF advanced the paper one line  If there was no CR  the next line would print as a staggered-step because LF didn t move the print head  FF advanced the paper to the next page  It typically also moved the print head to the start of the first line on the new page  but you might need CR for that  To be sure  most programmers coded CRFF instead of CRLF at the end of the last line on a page because an extra CR created by FF wouldn t matter

[newline] What are carriage return, linefeed, and form feed?

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