Mac text files use a single “Carriage-Return” as the “newline” character at the end of each line. By pressing the Enter key (in Insert Mode) inserts a <CR>. Line-Feed characters have no special meaning and are displayed as <LF>.
You must use additional care when editing Mac files. In particular you must be very careful with “cut and paste” operations between Mac and Windows/DOS files. For example, a multiple line block cut from a Mac file will become a single long line when pasted into a Windows/DOS file.
Because “regular expressions” were originally designed for UNIX text files with Line-Feed “newline” characters, you may have some trouble searching Mac files using some regular expressions.
To perform a “cut and paste” between Mac and Windows/DOS files, you may want to convert the Mac file into a Windows/DOS file.
of conversion choices.
More info over converting Mac files into a Windows/DOS files.