SIX is an alternative extension of the SIXEL bitmap graphics format. It was developed for terminals and printers by Digital Equipment Corporation (DEC). SIX actually means six pixels of which an image stored in the format consists. If you have a SIX file you want to view but you do not have an access to a DEC terminal, you need to convert it to a more popular format.

PCX is standard presentation graphics developed by ZSoft Korporation. Used graphics program ZSoft PC Paintbrush for MS-DOS, word processing and desktop publishing applications, such as Microsoft Word and Ventura Publisher. Not as popular analog BMP, although supported by specific graphics editors such as Adobe Photoshop, Corel Draw, GIMP and others.