▁specification ▁and ▁released ▁the ▁pat ent ▁to ▁the ▁O IN ▁members . ▁The ▁Linux ▁kernel ▁introduced ▁native ▁ex F AT ▁support ▁with ▁the ▁ 5 . 4 ▁release . ▁ ▁Techn ical ▁special ities ▁ ▁File ▁name ▁lookup ▁ ▁ex F AT ▁emp lo ys ▁a ▁filename ▁hash - based ▁lookup ▁phase ▁to ▁speed ▁certain ▁cases , ▁which ▁is ▁described ▁in ▁US ▁Pat ent ▁ 8 3 2 1 4 3 9 , ▁Quick ▁File ▁Name ▁Look up ▁Using ▁Name ▁Hash , ▁which ▁document ▁perhaps ▁contains ▁additional ▁details ▁helpful ▁in ▁understanding ▁of ▁the ▁file ▁system , ▁in ▁Append ix ▁A . ▁ ▁File ▁and ▁cluster ▁pre - al location ▁ ▁Like ▁N TF S , ▁ex F AT ▁can ▁pre - alloc ate ▁disk ▁space ▁for ▁a ▁file ▁by ▁just ▁mark ing ▁arbitrary ▁space ▁on ▁disk ▁as ▁' alloc ated '. ▁For ▁each ▁file , ▁ex F AT ▁uses ▁two ▁separate ▁ 6 4 - bit ▁length ▁fields ▁in ▁the ▁directory : ▁the ▁Valid ▁Data ▁L ength ▁( VD L ) ▁which ▁indicates ▁the ▁real ▁size ▁of ▁the ▁file , ▁and ▁the ▁physical ▁data ▁length . ▁ ▁To ▁provide ▁improvement ▁in ▁the ▁allocation ▁of ▁cluster ▁storage ▁for ▁a ▁new ▁file , ▁Microsoft ▁incorpor ated ▁a ▁method ▁to ▁pre - alloc ate ▁cont igu ous ▁clusters ▁and ▁by pass ▁the ▁use ▁of ▁updating ▁the ▁F AT ▁table ▁and ▁on ▁December ▁ 1 0 , ▁ 2 0 1 3 ▁the ▁US ▁pat ent ▁office ▁granted ▁pat ent ▁US 8 6 0 6 8 3