If in emacs you need a different file coding system (line terminator), for example you are on a windows system and need to type a unix like text file (or vice versa), you can easily convert the buffer coding system.

Dos to unix

M-x set-buffer-file-coding-system RET undecided-unix
save the file (C-x C-s)

or

C-x RET f undecided-unix
C-x C-f

Unix to dos

M-x set-buffer-file-coding-system RET undecided-dos
save the file (C-x C-s)

or

C-x RET f undecided-dos
C-x C-f