A number of writing systems have been used over the years for transcribing the language. Of these, the Somali alphabet is the most widely used, and has been the official writing script in Somalia since the government of former President of Somalia Mohamed Siad Barre formally introduced it in October 1972. The script was developed by the Somali linguist Shire Jama Ahmed specifically for the Somali language, and uses all letters of the English Latin alphabet except p, v and z. Besides Ahmed's Latin script, other orthographies that have been used for centuries for writing Somali include the long-established Arabic script and Wadaad's writing. Indigenous writing systems developed in the twentieth century include the Osmanya, Borama and Kaddare scripts, which were invented by Osman Yusuf Kenadid, Abdurahman Sheikh Nuur and Hussein Sheikh Ahmed Kaddare, respectively.