struct FNSAVE_FORMAT

typedef struct _FNSAVE_FORMAT
{
     ULONG ControlWord;
     ULONG StatusWord;
     ULONG TagWord;
     ULONG ErrorOffset;
     ULONG ErrorSelector;
     ULONG DataOffset;
     ULONG DataSelector;
     UCHAR RegisterArea[80];
} FNSAVE_FORMAT, *PFNSAVE_FORMAT;

Windows Vista Kernel Structures