Notepad, the text editor that ships with Windows, is not a complicated application. For many, this is its major advantage—by having virtually no features, it cannot go wrong—but especially for software developers, it has often proven an annoyance.

That’s because Notepad has traditionally only understood Windows line endings. Windows, Unix, and “classic” MacOS all use different conventions for indicating the end of a line of text. Windows does things correctly: it uses a pair of characters, the carriage return (CR) followed by the line feed (LF). Two characters are needed because they do different things: the CR moves the print head to the start of a line; the LF advances the paper by one line. Separating these is valuable, as it allows for effects such as underlining to be emulated: first print the text to be underlined, then issue a CR, and then print underscore characters.

Unix, however, uses a bare line feed to denote that a new line should be started. Classic MacOS (though not modern macOS) uses a bare carriage return for the same purpose. Given the meaning behind the CR and LF characters, these operating systems are both obviously wrong, but sometimes wrongness is allowed to prevail and persist.