When writing a file and this option is off and the 'binary' option is on, or 'fixeol' option is off, no will be written for the last line in the file. This option is automatically set or reset when starting to edit a new file, depending on whether file has an for the last line in the file. Normally you don't have to set or reset this option. When 'binary' is off and 'fixeol' is on the value is not used when writing the file. When 'binary' is on or 'fixeol' is off it is used to remember the presence of a for the last line in the file, so that when you write the file the situation from the original file can be kept. But you can change it if you want to.