This gives the of the current buffer, which is used for reading/writing the buffer from/to a file: dos unix mac When "dos" is used, CTRL-Z at the end of a file is ignored. See |file-formats| and |file-read|. For the character encoding of the file see 'fileencoding'. When 'binary' is set, the value of 'fileformat' is ignored, file I/O works like it was set to "unix". This option is set automatically when starting to edit a file and 'fileformats' is not empty and 'binary' is off. When this option is set, after starting to edit a file, the 'modified' option is set, because the file would be different when written. This option can not be changed when 'modifiable' is off. For backwards compatibility: When this option is set to "dos", 'textmode' is set, otherwise 'textmode' is reset.