-typedef uint16_t fill_t;
-typedef fill_t pgaddr_t;
-typedef uint16_t pgoff_t;
-typedef uint32_t mark_t;
-typedef uint8_t mark_roll_t;
-typedef uint8_t inode_t;
-typedef uint8_t seq_t;
-typedef rotating_t fcs_t;
+typedef uint16_t fill_t; ///< Type for keeping trace of space filled inside a page
+typedef fill_t pgaddr_t; ///< Type for addressing space inside a page
+typedef uint16_t pgcnt_t; ///< Type for counting pages on disk
+typedef pgcnt_t pgoff_t; ///< Type for counting pages inside a file
+typedef uint32_t mark_t; ///< Type for marking pages as free
+typedef uint8_t inode_t; ///< Type for file inodes
+typedef uint8_t seq_t; ///< Type for page seq number
+typedef rotating_t fcs_t; ///< Type for header FCS.