The Koran is the word of God as revealed to Muhammed on the road to Medina around AD 600.
Muslims believe the Koran to be the exact words as spoken by God to Muhammed.
But in AD 633 a large number of Huffaz, men who memorise and recite the Koran, were killed in various battles and so the Muslim community began to use writing to communicate. The Arabic script spread to three continents following the founding of Islam.