Visual LISP supports the creation of backup files for each file loaded by the text editor.
A backup file is created when you save the file for the first time. Backup files have the same name as the original file, except the file extension begins with an underscore (_) and is followed by the first two characters of the original extension. For example, the backup file for drawline.lsp would be drawline._ls.
The automatic creation of a backup file is an option set in the General Options dialog.