The internal binary data formats of the VAX and SUN systems are different which makes it impossible to share data files ( e.g. image or table). The SUN systems store data starting with the most significant bits ( i.e. big endian) and use IEEE floating point format while VAX's are byte swapped and have a proprietary floating point format.
In order to exchange data files between these systems it is necessary to use a machine independent format e.g. FITS. For this reason and because internal MIDAS data structures may change, it is strongly recommended to save data in FITS format.