 This system image can be the form in which executable programs are distributed—this method has often been used by programs (such as TeX and Emacs) largely implemented in Lisp, Smalltalk, or idiosyncratic languages to avoid spending time repeating the same initialization work every time they start up.Similar, Lisp Machines were booted from Lisp images, called Worlds.The World contains the complete operating system, its applications and its data in a single file.