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In computing, a newline, also known as a line ending, end of line (EOL), or line break, is a special character or sequence of characters signifying the end of a line of text and the start of a new line. The actual codes representing a newline vary across operating systems, which can be a problem when exchanging text files between systems with different newline representations. The concepts of line feed (LF) and carriage return (CR) are closely associated, and can be either considered separately or lumped 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 lump them together as one event. This is why a newline in character encoding can be defined as LF and CR combined into one (CR+LF, CRLF, LF+CR, LFCR). Two ways to view newlines, both of which are self-consistent, are that newlines ''separate'' lines or that they ''terminate'' lines. If a newline is considered a separator, there will be no newline after the last line of a file. Some programs have problems processing the last line of a file if it is not terminated by a newline. On the other hand, programs that expect newline to be used as a separator will interpret a final newline as starting a new (empty) line. In text intended primarily to be read by humans using software which implements the word wrap feature, a newline character typically only needs to be stored if a line break is required independent of whether the next word would fit on the same line, such as between paragraphs and in vertical lists. Therefore, in the logic of word processing, newline is used as a paragraph break and is known as a "hard return", in contrast to "soft returns", which are the dynamic ones created by word wrap that are changeable with each display instance. A separate control character called "manual line break" exists for forcing line breaks inside a single paragraph. ==Representations== Software applications and operating systems usually represent a newline with one or two control characters: *Systems based on ASCII or a compatible character set use either LF (Line feed, '\n', 0x0A, 10 in decimal) or CR (Carriage return, '\r', 0x0D, 13 in decimal) individually, or CR followed by LF (CR+LF, '\r\n', 0x0D0A). These characters are based on printer commands: The line feed indicated that one line of paper should feed out of the printer thus instructed the printer to advance the paper one line, and a ''carriage return'' indicated that the printer carriage should return to the beginning of the current line. Some rare systems, such as QNX before version 4, used the ASCII RS (record separator, 0x1E, 30 in decimal) character as the newline character. * *LF: Multics, Unix and Unix-like systems (Linux, OS X, FreeBSD, AIX, Xenix, etc.), BeOS, Amiga, RISC OS, and others * *CR: Commodore 8-bit machines, Acorn BBC, ZX Spectrum, TRS-80, Apple II family, Mac OS up to version 9, and OS-9 * *RS: QNX pre-POSIX implementation * *0x9B: Atari 8-bit machines using ATASCII variant of ASCII (155 in decimal) * *CR+LF: Microsoft Windows, DOS (MS-DOS, PC DOS, etc.), DEC TOPS-10, RT-11, CP/M, MP/M, Atari TOS, OS/2, Symbian OS, Palm OS, Amstrad CPC, and most other early non-Unix and non-IBM OSes * *LF+CR: Acorn BBC and RISC OS spooled text output. *EBCDIC systems—mainly IBM mainframe systems, including z/OS (OS/390) and i5/OS (OS/400)—use NL (New Line, 0x15)〔IBM System/360 Reference Data Card, Publication GX20-1703, IBM Data Processing Division, White Plains, NY〕 as the character combining the functions of line-feed and carriage-return. The equivalent UNICODE character is called NEL (Next Line). Note that EBCDIC also has control characters called CR and LF, but the numerical value of LF (0x25) differs from the one used by ASCII (0x0A). Additionally, some EBCDIC variants also use NL but assign a different numeric code to the character. *Operating systems for the CDC 6000 series defined a newline as two or more zero-valued six-bit characters at the end of a 60-bit word. Some configurations also defined a zero-valued character as a colon character, with the result that multiple colons could be interpreted as a newline depending on position. *ZX80 and ZX81, home computers from Sinclair Research Ltd used a specific non-ASCII character set with code NEWLINE (0x76, 118 decimal) as the newline character. *OpenVMS uses a record-based file system, which stores text files as one record per line. In most file formats, no line terminators are actually stored, but the Record Management Services facility can transparently add a terminator to each line when it is retrieved by an application. The records themselves could contain the same line terminator characters, which could either be considered a feature or a nuisance depending on the application. *''Fixed line length'' was used by some early mainframe operating systems. In such a system, an implicit end-of-line was assumed every 72 or 80 characters, for example. No newline character was stored. If a file was imported from the outside world, lines shorter than the line length had to be padded with spaces, while lines longer than the line length had to be truncated. This mimicked the use of punched cards, on which each line was stored on a separate card, usually with 80 columns on each card, often with sequence numbers in columns 73–80. Many of these systems added a carriage control character to the start of the ''next'' record; this could indicate whether the next record was a continuation of the line started by the previous record, or a new line, or should overprint the previous line (similar to a CR). Often this was a normal printing character such as "#" that thus could not be used as the first character in a line. Some early line printers interpreted these characters directly in the records sent to them. Most textual Internet protocols (including HTTP, SMTP, FTP, IRC, and many others) mandate the use of ASCII CR+LF ('\r\n', 0x0D 0x0A) on the protocol level, but recommend that tolerant applications recognize lone LF ('\n', 0x0A) as well. Despite the dictated standard, many applications erroneously use the C newline escape sequence '\n' (LF) instead of the correct combination of carriage return escape and newline escape sequences '\r\n' (CR+LF) (see section Newline in programming languages below). This accidental use of the wrong escape sequences leads to problems when trying to communicate with systems adhering to the stricter interpretation of the standards instead of the suggested tolerant interpretation. One such intolerant system is the qmail mail transfer agent that actively refuses to accept messages from systems that send bare LF instead of the required CR+LF.〔(cr.yp.to )〕 FTP has a feature to transform newlines between CR+LF and the native encoding of the system (e.g., LF only) when transferring text files. This feature must not be used on binary files. Often binary files and text files are recognised by checking their filename extension; most command-line FTP clients have an explicit command to switch between binary and text mode transfers. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Newline」の詳細全文を読む スポンサード リンク
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