The numerical references for the ideograms were originally devised by Ventris and Bennett and divided into functional groups corresponding to the breakdown of Bennett's index. The groups are numbered beginning 100, 110, 120 etc., with some provision of spare numbers for future additions; the official CIPEM numberings used today are based on Ventris and Bennett's numbering, with the provision that three or four letter codes (written in small capitals), based on Latin words that seemed relevant at the time, are used where the meanings are known and agreed. Unicode (as of version 5.0) encodes 123 Linear B ideograms.