Editing File Transfer Protocol (section)

===Data types===
While transferring data over the network, five data types are defined:<ref name="tcpip" /><ref name="net+" /><ref name="clark" />
* [[ASCII]] (TYPE A): Used for text. Data is converted, if needed, from the sending host's character representation to [[Extended ASCII|"8-bit ASCII"]] before transmission, and (again, if necessary) to the receiving host's character representation, including [[newline]]s. As a consequence, this mode is inappropriate for files that contain data other than ASCII.
* Image (TYPE I, commonly called [[Binary data|Binary]] mode): The sending machine sends each file [[byte]] by byte, and the recipient stores the [[bytestream]] as it receives it. (Image mode support has been recommended for all implementations of FTP).
* [[EBCDIC]] (TYPE E): Used for plain text between hosts using the EBCDIC character set.
* Local (TYPE L ''n''): Designed to support file transfer between machines which do not use 8-bit bytes, e.g. [[36-bit computing|36-bit systems]] such as DEC [[PDP-10]]s. For example, "TYPE L 9" would be used to transfer data in 9-bit bytes, or "TYPE L 36" to transfer 36-bit words. Most contemporary FTP clients/servers only support L 8, which is equivalent to I.
* [[Unicode]] text files using [[UTF-8]] (TYPE U): defined in an expired [[Internet Draft]]<ref>{{Cite IETF|last=Klensin|first=John|title=FTP TYPE Extension for Internationalized Text|draft=draft-klensin-ftpext-typeu-00|access-date=2020-06-09}}</ref> which never became an RFC, though it has been implemented by several FTP clients/servers.

Note these data types are commonly called "modes", although ambiguously that word is also used to refer to active-vs-passive communication mode (see above), and the modes set by the FTP protocol MODE command (see below).

For text files (TYPE A and TYPE E), three different format control options are provided, to control how the file would be printed:
* Non-print (TYPE A N and TYPE E N) – the file does not contain any carriage control characters intended for a printer
* [[Telnet]] (TYPE A T and TYPE E T) – the file contains Telnet (or in other words, ASCII C0) carriage control characters (CR, LF, etc)
* [[ASA carriage control characters|ASA]] (TYPE A A and TYPE E A) – the file contains ASA carriage control characters
These formats were mainly relevant to [[line printer]]s; most contemporary FTP clients/servers only support the default format control of N.