diff --git a/src/fs-filo.ads b/src/fs-filo.ads
index 4171b79..b9e5742 100644
--- a/src/fs-filo.ads
+++ b/src/fs-filo.ads
@@ -1,3 +1,22 @@
+with Interfaces;
+with Interfaces.C;
+
+use Interfaces.C;
+
 package FS.FILO is
 
+private
+   type Partition_Length is range 0 .. Interfaces.Unsigned_64'Last;
+
+   function Part_Length return Partition_Length;
+
+   type File_Length is range 0 .. int'Last; -- Should be higher, fix FILO first
+   subtype File_Offset is File_Length range 0 .. File_Length'Last - 1;
+
+   function File_Max return File_Length;
+   procedure Set_File_Max (Len : File_Length);
+
+   function File_Pos return File_Offset;
+   procedure Set_File_Pos (Off : File_Offset);
+
 end FS.FILO;