Newline

Newline (frequently called line ending, end of line (EOL), line feed, or line break) is a control character or sequence of control characters in a character encoding specification (e.g. ASCII or EBCDIC) that is used to signify the end of a line of text and the start of a new one. Some text editors set this special character when pressing the ↵ Enter key. When displaying (or printing) a text file, this control character causes the text editor to show the following characters in a new line. In the mid-1800s, long before the advent of teleprinters and teletype machines, Morse code operators or telegraphists invented and used Morse code prosigns to encode white space text formatting in formal written text messages. In particular the Morse prosign represented by the concatenation of two literal textual Morse code 'A' characters sent without the normal inter-character spacing is used in Morse code to encode and indicate a new line in a formal text message. Later in the age of modern teleprinters standardized character set control codes were developed to aid in white space text formatting. ASCII was developed simultaneously by the International Organization for Standardization (ISO) and the American Standards Association (ASA), the latter being the predecessor organization to American National Standards Institute (ANSI). During the period of 1963 to 1968, the ISO draft standards supported the use of either .mw-parser-output .monospaced{font-family:monospace,monospace}CR+LF or LF alone as a newline, while the ASA drafts supported only CR+LF. The sequence CR+LF was commonly used on many early computer systems that had adopted Teletype machines—typically a Teletype Model 33 ASR—as a console device, because this sequence was required to position those printers at the start of a new line. The separation of newline into two functions concealed the fact that the print head could not return from the far right to the beginning of the next line in time to print the next character. Any character printed after a CR would often print as a smudge in the middle of the page while the print head was still moving the carriage back to the first position. 'The solution was to make the newline two characters: CR to move the carriage to column one, and LF to move the paper up.' In fact, it was often necessary to send extra characters—extraneous CRs or NULs—which are ignored but give the print head time to move to the left margin. Many early video displays also required multiple character times to scroll the display. On such systems, applications had to talk directly to the Teletype machine and follow its conventions since the concept of device drivers hiding such hardware details from the application was not yet well developed. Therefore, text was routinely composed to satisfy the needs of Teletype machines. Most minicomputer systems from DEC used this convention. CP/M also used it in order to print on the same terminals that minicomputers used. From there MS-DOS (1981) adopted CP/M's CR+LF in order to be compatible, and this convention was inherited by Microsoft's later Windows operating system. The Multics operating system began development in 1964 and used LF alone as its newline. Multics used a device driver to translate this character to whatever sequence a printer needed (including extra padding characters), and the single byte was more convenient for programming. What seems like a more obvious choice—CR—was not used, as CR provided the useful function of overprinting one line with another to create boldface and strikethrough effects. Perhaps more importantly, the use of LF alone as a line terminator had already been incorporated into drafts of the eventual ISO/IEC 646 standard. Unix followed the Multics practice, and later Unix-like systems followed Unix. This created conflicts between Windows and Unix-like OSes and files composed on one OS can't be properly formatted or interpreted by another OS (Like a bash script written in Notepad for example). The concepts of line feed (LF) and carriage return (CR) are closely associated, and can be considered either separately or together. In the physical media of typewriters and printers, two axes of motion, 'down' and 'across', are needed to create a new line on the page. Although the design of a machine (typewriter or printer) must consider them separately, the abstract logic of software can combine them together as one event. This is why a newline in character encoding can be defined as LF and CR combined into one (commonly called CR+LF or CRLF).