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Compare the difference between carriage return and line feed
Compare the difference between carriage return and line feed
In fact, we don’t really care about line feeds and carriage returns, so the difference between the two is not very clear. During daily development, we may encounter some file processing problems, and various problems will occur on different operating systems. pit. So what are the differences between carriage return and line feed? Today we will summarize it.
1. Origin
Before computers appeared, there was a mechanical typewriter called Teletype Model 33, which could type 10 characters per second. But there is a problem with it, that is, it takes 0.2 seconds to type a line and break it, which is enough to type two characters. If a new character is transmitted during these 0.2 seconds, this character will be lost.
So, the developers thought of a way to solve this problem, which was to add two characters to indicate the end of each line. One is called "carriage return" and tells the typewriter to position the print head at the left edge without rolling the roller; the other is called "line feed" and tells the typewriter to roll the roller one space without changing the horizontal position.
This is the origin of "line feed" and "carriage return".
2. Use
Later, the computer was invented, and these two concepts were transferred to the computer. At that time, memory was expensive, and some scientists thought it was too wasteful to add two characters at the end of each line. Just add one. So, there was a disagreement.
Carriage Return\r The original meaning is that the cursor returns to the beginning of the line, r is the English return, the control character can be written as CR, that is, Carriage Return
Newline\n The original meaning is that the cursor goes to the next line ( (not necessarily to the beginning of the next line), the English newline of n, the control character can be written as LF, that is, Line Feed
symbol ASCII code Meaning
\n 10 10 Line feed NL
\ r 13 Enter Cr
## Different characters have different characters in different operating systems. For example, under Win system, these two characters are the original meaning of performance. The cursor moves to the next line and returns to the beginning of the line. On MAC, \r means returning to the beginning of the line and going to the next line. The definition of the ENTER key is related to the operating system. The commonly used Enter is the sum of two. Meanings under different operating systems: \n: UNIX system end-of-line terminator\n\r: window system end-of-line terminator\ r: MAC OS system end-of-line character A problem we often encounter is that when files under Unix/Mac systems are opened in Windows, all text will become one line; while files in Windows will be opened in Unix If opened under /Mac, there may be an extra ^M symbol at the end of each line. 3. Soft carriage return and hard carriage returnExpand some knowledge about carriage return. Hard carriage return is generated by pressing Enter. It not only breaks lines but also plays the role of paragraph separation. Soft return is generated by using Shift + Enter. It breaks lines but does not break paragraphs. That is, the two paragraphs of text before and after belong to the same "paragraph" in Word. You will appreciate this when applying the format. Soft carriage return can greatly reduce the line spacing between the two lines before and after it, because it is not a paragraph mark and must be distinguished from the legal paragraph mark-hard carriage return. The html code for hard carriage return is..
, and the content of the paragraph is sandwiched inside, while the code for soft carriage return is very concise:. If the text of the web page is copied into Word, the hard return will turn into a curved arrow, and the soft return will turn into a downward arrow.
The above is the detailed content of Compare the difference between carriage return and line feed. For more information, please follow other related articles on the PHP Chinese website!
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