Assalam oalaikum,
The main reason behind the revelation of Al- Quran was to make it a guide for the entire world till the Day of Judgment. Hence, after the revelation of the Wahi it became imperative to write it down in order to protect Allah (swt)’s Divine message.
For the safeguard and preservation of the Quranic Wahi two techniques were adopted, namely Hifz (memorizing the entire Quran) and second, writing.
Allah (swt) says in The Holy Quran: "And indeed We have made The Quran easy to remember, so is there anyone who will memorize it?"
The Arabs by had very powerful memories. Some Egyptian scientists had conducted experiments to understand the advantage of eating dates with milk. Much to their amazement they found that milk and dates prevents loss of memory and increases one’s IQ level. So secret behind the phenomenal memories of the Sahaabas (ra) was discovered at last because milk, dates etc were their staple diet.
34 Saba (Saba, Sheba),سورة سبأ
35 Fatir (Orignator),سورة فاطر
36 Ya-Seen (Ya-seen),سورة يس
remember me in your prayers
amel soname