But in Unix “\n” is a single byte, and in DOS it is 2. So they introduced text and binary modes for files on DOS. Behind the scenes the library will handle the extra byte. This is not necessary in Unix.
I used to have to be careful about importing files to DOS. Did the file come from Unix?
I think you are talking about carriage return linefeed pair (CRLF or \r\n),
These control codes go back to line printers. Linefeed advances the paper one line and carriage return moves the print head to the left.
In binary mode. In text mode if you printf(“Hello World\n”) you get CRLF because that’s how text works on DOS. Unix had the convention of only requiring the LF for text. And Unix didn’t have text/binary modes. That’s the compatibility hack on DOS.
>These control codes go back to line printers.
Back to teletypes even. Believe me, I go back to line printers.
Note that printf(), which you use in your example, is a C library function that writes writes to a predefined text mode stream. So it follows the same rules.
I wasn't able to dig up the source code of a vintage DOS compiler's C library in a few minutes of looking, so I can't prove it right now, but this section of the C standard (7.21.2 - Streams) hints that my recollection is correct:
https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf#p...
*(On systems where the char type is one byte, of course, which is the case for DOS C compilers.)
Sending a carriage return and linefeed to a TTY 33 and then printing works fine. Doing them in the opposite order, if the carriage is to the right of the page, will result in a linefeed (platen rotation) happening quickly, then the carriage starting to move left to the beginning of the next line, and then the next printed character will print wherever the carriage happens to be at the time - not yet to the left. So you will be missing a character at the beginning of the line because it's in between the two lines in an unexpected column-ish.
I have run into (in my mind, "hipster") code where the programmer for some reason reversed the order of CR and LF.
Text inside a computer doesn't need any of that just to signal a newline. UNIX chose to use a single line feed character as a line separator because there was no good reason to use two. MacOS chose a single carriage return for similar reasons. Anything going out to a printer or teletype would run through a device driver that would turn the newline character into whatever the device expects.
Windows copied DOS which copied CP/M which was a very basic program loader for 8-bit machines and didn't really have "drivers" like we think of them today. I'm guessing here, but I imagine they chose the teletype combo because that's what most serial printers understood and printing was a major use case for those machines. That was probably the right choice for CP/M, but I can't imagine Microsoft would choose it if they were developing Windows from scratch today.
