Editing File Transfer Protocol (section)

===File structures===
File organization is specified using the STRU command. The following file structures are defined in section 3.1.1 of RFC959:
* '''F''' or FILE structure (stream-oriented). Files are viewed as an arbitrary sequence of bytes, characters or words. This is the usual file structure on Unix systems and other systems such as CP/M, MS-DOS and Microsoft Windows. (Section 3.1.1.1)
* '''R''' or RECORD structure (record-oriented). Files are viewed as divided into records, which may be fixed or variable length. This file organization is common on mainframe and midrange systems, such as MVS, VM/CMS, OS/400 and VMS, which support [[record-oriented filesystem]]s.
* '''P''' or PAGE structure (page-oriented). Files are divided into pages, which may either contain data or metadata; each page may also have a header giving various attributes. This file structure was specifically designed for [[TENEX (operating system)|TENEX]] systems, and is generally not supported on other platforms. RFC1123 section 4.1.2.3 recommends that this structure not be implemented.

Most contemporary FTP clients and servers only support STRU F. STRU R is still in use in mainframe and minicomputer file transfer applications.