A number of writing systems have been used to transcribe the Somali language. Of these, the Somali Latin alphabet is the most widely used. It has been the official writing script in Somalia since the Supreme Revolutionary Council formally introduced it in October 1972, and was disseminated through a nationwide rural literacy campaign. Prior to the twentieth century, the Arabic script was used for writing Somali. An extensive literary and administrative corpus exists in Arabic script. It was the main script historically used by the various Somali sultans to keep records. Writing systems developed locally in the twentieth century include the Osmanya, Borama and Kaddare scripts.