struct NodeDescriptor {
        SInt32          ndFLink;        forward link (LongInt)
        SInt32          ndBLink;        backward link (LongInt)
        SInt8           ndType;         node type (SignedByte)
        SInt8           ndNHeight;      node level (SignedByte)
        SInt16          ndNRecs;        number of records in node (Integer)
        SInt16          ndResv2;        reserved (Integer)
};
