when I was an apprentice in the Royal Signals many (50) years ago, teletypes and typewriters had "Carriage" with the printing head on them. When you pressed RETURN the Carriage would fly to the left. Hence Carriage Return (CR). You could just return the Carriage, but on mechanical typewriters, you'd use the Lever (much like a tremolo lever on an electric guitar) which would also do the Line Feed. Your next question is why would you not want the line feed? heh heh well in those days to delete characters we'd do a CR then use a Tip-ex-like paper in between the hammerheads and paper and type the same keys to over-write with white ink. Some fancy typewriters had a key you could press. So there you go.

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

看看维基百科:

基于ASCII或兼容字符集的系统分别使用LF(换行，'\n'， 0x0A，十进制10)或CR(回车，'\r'， 0x0D，十进制13)，或CR后跟LF (CR+LF, 0x0D 0x0A)。这些字符是基于打印机命令的:换行指示一行纸应该从打印机输出，回车指示打印机的回车应返回到当前行的开头。

Apart from above information, there is still an interesting history of LF (\n) and CR (\r). [Original author : 阮一峰 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.

于是科学家们找到了解决这个问题的方法，他们在每行后面加了两个结尾字符，一个是“回车”，这是告诉打印机将打印头移到左边。另一个是“换行”，它告诉打印机将纸张上移一行。

后来，计算机变得流行起来，这两个概念都用在了计算机上。当时的存储设备很贵，所以有科学家说每行末尾加两个字很贵，一个就够了，所以用哪个就有一些争论。

在UNIX/Mac和Linux中，'\n'被放在每行的末尾，在Windows中，'\r\n'被放在每行的末尾。这种使用的结果是，如果在Windows中打开，UNIX/Mac中的文件将显示在一行中。而Windows中的文件如果在UNIX或Mac中打开，则每行末尾会有一个^M。

when I was an apprentice in the Royal Signals many (50) years ago, teletypes and typewriters had "Carriage" with the printing head on them. When you pressed RETURN the Carriage would fly to the left. Hence Carriage Return (CR). You could just return the Carriage, but on mechanical typewriters, you'd use the Lever (much like a tremolo lever on an electric guitar) which would also do the Line Feed. Your next question is why would you not want the line feed? heh heh well in those days to delete characters we'd do a CR then use a Tip-ex-like paper in between the hammerheads and paper and type the same keys to over-write with white ink. Some fancy typewriters had a key you could press. So there you go.

\r是回车，光标向后移动，就像我要做-一样

printf("stackoverflow\rnine")
ninekoverflow

表示已将光标移到“stackoverflow”的开头，并覆盖开始的4个字符，因为“nine”有4个字符长。

\n是新行字符，它改变行并将光标移到新行开头，如-

printf("stackoverflow\nnine")
stackoverflow
nine

\f是进给，它的用途已经过时了，但它被用于缩进

printf("stackoverflow\fnine")
stackoverflow
             nine

如果我这样写

printf("stackoverflow\fnine\fgreat")
stackoverflow
             nine
                 great