MBM is shortened from MultiBitMap which, as the name suggests, is a container for a set of bitmap images. The contained bitmaps are not stored verbatim. Rather, each one is stored with a modified bitmap header with no data compression or with 8-, 12-, 16-, or 24-bit RLE compression. MBM files are used by most Symbian GUI applications to store their graphical content. See also Symbian OS Symbian Ltd. Symbian installation source Graphics file formats