MS03 is the signature of the tag used by Windows to track the output resolution dot size. For a more complete discussion of tags and signatures, see the ICC version 3.0 specification. The data size is of type icUInt64Number (an unsigned 64-bit identifier value according to the ICC specification). The purpose of this tag is to identify the current raster resolution that the printer driver is configured for and map it to the appropriate ICC profile. It corresponds to the dmPrintQuality and dmYResolution members of the printer driver's DEVMODE structure. These map to the high and low double-word values in the eight-byte value respectively. Note that since the DEVMODE values are each a word quantity, the high word of each double-word is unused/reserved. They must be an exact match to map correctly. A more detailed discussion of run-time profile selection is given in a later section. If this tag is not defined in the profile, a key value of "ResolutionUnknown" is placed in the registry at installation time. For a complete description of values for this tag, see the Win32 SDK or Windows 95 DDK documentation.