The Arabic alphabet is an offshoot of the early Semitic one, probably originated about the 4th century AD. It has 28 letters and is based on 18 distinct shapes plus dots written above or below those shapes. Arabic is written from right to left, and the letters are joined in writing. It spread to such languages as Persian, Pashto, and Urdu and is generally used by the Islamic world in parts of Asia and Africa, and in southern Europe. Arabic is written in either of two forms: Kufic, a heavy, bold, formal script, was devised at the end of the 7th century; or Naskhi, a cursive form and the parent of modern Arabic writing. (Encarta Encyclopedia)
