What was justinian code based on?

Code of Justinian, Latin Codex Justinianus, formally Corpus Juris Civilis ("Body of Civil Law"), the collections of laws and legal interpretations developed under the sponsorship of the Byzantine emperor Justinian I from ad 529 to 565. Strictly speaking, the works did not constitute a new legal code. Rather, Justinian’s committees of jurists provided basically two reference works containing collections of past laws and extracts of the opinions of the great Roman jurists. Also included were an elementary outline of the law and a collection of Justinian’s own new laws.