carriagereturn

Carriage return, often abbreviated CR, is a control character or mechanism used to move the cursor to the beginning of the current line. Historically, on typewriters and early printers, the carriage held the paper and mechanical actions separated the tasks of returning to the left margin (carriage return) and advancing the paper to the next line (line feed). The combination of these actions allowed new lines to be prepared for typing.

In digital systems, CR has a defined representation: the ASCII code 13 (0x0D) and the Unicode code point U+000D. In many programming languages, it is written as the escape sequence \r. The concept is still tied to the original mechanical idea of resetting the horizontal position of the print mechanism.

Line-ending conventions differ across platforms. Windows uses a two-character sequence CR followed by line feed (CRLF, \r\n) to denote a new line. Unix-like systems use a single line feed (LF, \n). Classic macOS used CR alone, but modern macOS follows the Unix convention. These differences can cause text-processing issues when transferring files between systems, often requiring normalization of end-of-line markers.

In modern networking and internet protocols, CRLF is commonly used to terminate lines, notably in HTTP headers and SMTP commands. In programming and text processing, CR may appear within strings or be part of line-ending sequences, and editors or tools often provide conversions between CR, LF, and CRLF.

See also: line feed, newline, end-of-line, text encoding.