The Map Overlay and Statistical System (MOSS), is a GIS software technology. Development of MOSS began in late 1977 and was first deployed for use in 1979. MOSS represents a very early public domain, open source GIS development - predating the better known GRASS by 5 years. MOSS utilized a polygon based data structure in which point, line, and polygon features could all be stored in the same file. The user interacted with MOSS via a command line interface.