BMP,BMX,GIF,WBMP formats - open files with these extensions. Format BM16x64 - blackwhite BMP 16x64 pixels, it is template for BMX-animation. When you open 1664 picture - paintcad can show it to you as 3232 pixels separated to 4 frames. It is conveniently for editing. Detailed about drawing 4-framed BMX animations see at chapter 'Painting'.