FC (File Character position):

A four-byte integer which is the byte offset of a character (or other object) from the beginning of a stream of the docfile. Before a file has been edited(i.e. in a full saved Word document), CPs can be transformed into FCs by adding the FC coordinate of the beginning of a document's text stream to the CP. After a file has been edited (i.e. in a fast-saved Word document), the mapping from CP to FC is recorded in the piece table (see below)