Ulum Al Quran : An Introduction To The Sciences Of Quran by Ahmad von Denffer

The Arabic letters, as we know them today, are made up of lines and points. The latter are called i'jam. The ancient Arabic script did not have them, but consisted of strokes only.

The addition of diacritical points to the plain writing of strokes helped to distinguish the various letters which could be easily mixed up.

Example: XXX XXX Without dots this word cannot be easily recognized. With i'jam, the letters of this word can easily be distinguished.

Although the i'jam (diacritical points) were already known in pre-Islamic times, they were rarely used. The very early copies of the Qur'anic manuscripts (and Arabic writing in general) did not have these signs. They were apparently introduced into the Qur'anic script during the time of the fifth Umayyad Caliph, 'Abd al-Malik bin Marwan (66-86H/685- 705) and the governorship of Al-Hajjaj in Iraq, when more and more Muslims began to read and study the Qur'an, some of whom did not know much of the Qur'an, and others were of non-Arab origin. It is said of the well-known tabi'l Al-Du'all that he was the first to introduce these points into the Qur'anic text.