The History Of Carriage Return Line Feed
| 18th July 2010 |
Most of us developers (especially Windows developers) wonder why an end-of-line is represented by <carriage return><line feed> in Windows text files. What does <carriage return> or <line feed> exactly mean?
In the early stages before computers, there existed a device known as the TeleType. The TeleType contained a keyboard, printer, and paper tape reader/punch. It could transmit messages over telephones using a modem at a rate of 10 characters per second.
But TeleType had a problem. It took 0.2 seconds to move the printhead from the right side to the left. 0.2 seconds is two character times. If a second character came while the printhead was in the middle of a return, that character was lost.
The TeleType people solved this problem by making end-of-line two characters: <carriage return> to position the printhead at the left margin, and <line feed> to move the paper up one line. That way the <line feed> “printed” whilethe printhead was racing back to the left margin.
When the early computers came out, some designers realized that using two characters for end-of-line wasted storage. Some picked <line feed> for their end-of-line, and some chose <carriage return>. Some of the die-hards stayed with the two-character sequence.
Unix uses <line feed> for end-of-line. The newline character n is code 0xA (LF or <line feed>). MS-DOS/Windows uses the two characters <carriage return><line feed>. So if you are transferring text files from a Unix machine to Windows, you have to use some conversion utility eg. unix2dos for stripping the <carriage return> character from the files.
Further reading:
How do I convert between Unix and Windows text files?
Newline Character
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