1. Mohammed was illiterate was a well known fact.'In the ancient times, when writing was scarcely used, memory and oral transmission was exercised and strengthened to a degree now almost unknown' relates Michael Zwettler.
Prophet Muhammad (S) encouraged his companions to learn and teach the Quran:
'Some of the companions who memorized the Quran were: 'Abu Bakr, Umar, Uthman, Ali, Ibn Masud, Abu Huraira, Abdullah bin Abbas, Abdullah bin Amr bin al-As, Aisha, Hafsa, and Umm Salama'. Many Quranic memorizers (Qurra) were present during the lifetime of the Prophet and afterwards through out the then Muslim world. 'Over the centuries of the Islamic Era, there have arisen throughout the various regions of the Islamic world literally thousands of schools devoted specially to the teaching of the Quran to children for the purpose of memorization. These are called, in Arabic, katatib (singular: Kuttab). It is said that the Caliph 'Umar (634-44) first ordered the construction of these schools in the age of the great expansion'.
Second generation:
"…Quranic schools were set up everywhere. As an example to illustrate this I may refer to a great Muslim scholar, of the second Muslim generation, Ibn 'Amir, who was the judge of Damascus under the Caliph Umar Ibn 'Abd Al-Aziz. It is reported that in his school for teaching the Quran there were 400 disciples to teach in his absence".
He did not have to memorise thousands of words, since the verses were revealed over 23 years, not in one day
2. Written text of the Quran:
Zaid is reported to have said: 'We use to compile the Qur'an from small scraps in the presence of the Apostle'. 'Besides the official manuscripts of the Quran kept with the Prophet, many of his companions use to possess their own written copies of the revelation'. 'A list of Companions of whom it is related that they had their own written collections included the following: Ibn Mas'ud, Ubay bin Ka'b, Ali, Ibn Abbas, Abu Musa, Hafsa, Anas bin Malik, Umar, Zaid bin Thabit, Ibn Al-Zubair, Abdullah ibn Amr, Aisha, Salim, Umm Salama, Ubaid bin Umar'. 'Aisha and Hafsa, the wives of the Prophet had their own scripts written after the Prophet had died'
'The Prophet, while in Madinah, had about 48 scribes who use to write for him'.
At the battle of Yamama (633 CE), six months after the death of the Prophet, a number of Muslims, who had memorized the Quran were killed. Hence it was feared that unless a written official copy of the Quran were prepared, a large part of revelation might be lost.
Narrated Zaid bin Thabit al-Ansari, one of the scribes of the Revelation: Abu Bakr sent for me after the casualties among the warriors (of the battle) of Yamama (where a great number of Qurra (memorizers of the Quran, were killed). Umar was present with Abu Bakr who said: "Umar has come to me and said, the people have suffered heavy casualties on the day of (the battle) of Yamama, and I am afraid that there will be some casualties among the Qurra at other places, whereby a large part of the Quran may be lost, unless you collect it (in one manuscript, or book)…so Abu Bakr said to me (Zaid bin Thabit): You are a wise young man and we do not suspect you (of telling lies or of forgetfulness) and you used to write the Divine Inspiration for Allah's Apostle. Therefore, look for the Qur'an and collect it (in one manuscript)'…So I started locating the Quranic material and collecting it from parchments, scapula, leafstalks of date palms and from the memories of men (who know it by heart)…"
Now, a committee was formed to under take the task of collecting the written Quranic material in the form of a book. The committee was headed by Zaid bin Thabit, the original scribe of the Prophet, who was also a memorizer of the complete Quran.
'…Zaid bin Thabit had committed the entire Quran to memory…'
The compilers in this committee, in examining written material submitted to them, insisted on very stringent criteria as a safeguard against any errors.
1. The material must have been originally written down in the presence of the Prophet; nothing written down later on the basis of memory alone was to be accepted.
2. The material must be confirmed by two witnesses, that is to say, by two trustworthy persons testifying that they themselves had heard the Prophet recite the passage in question.
'The manuscript on which the Qur'an was collected, remained with Abu Bakr till Allah took him unto Him, and then with Umar (the second successor), till Allah took him unto Him, and finally it remained with Hafsa, 'Umar's daughter (and wife of the Prophet)'.
This copy of the Quran, prepared by the committee of competent companions of the Prophet (which included Memorizers of the Quran) was unanimous approved by the whole Muslim world. If they committee would have made a error even of a single alphabet in transcribing the Quran, the Qurra (memorizers of the Quran) which totaled in the tens of hundreds would have caught it right away and correct it.
3. Official copy of the Quran:
During Mohammed's time there were several variant recitations of the Quran which Uthman decided may lead to disunity among Muslims (there was already a Sunni-Shia split, and there were problems brewing between the Syrians and Iraqis of the time), so he called for an ijma or council and they decided on the Qureysh form and burned the rest.
Again a very stringent criteria was set up by this Committee to prevent any alteration of the Revelation.
1. The earlier recension (Original copy prepared by Abu Bakr) was to serve as the principal basis of the new one.
2. Any doubt that might be raised as to the phrasing of a particular passage in the written text was to be dispelled by summoning persons known to have learned the passage in question from the Prophet.
3. Uthman himself was to supervise the work of the Council.
4. The copy of Hamsa was always kept separately, so as not be lost or destroyed by war and fire. This copy was kept by Uthman. The 5 copies he made were for the cities of Makka, Damascus, Kufa, Basra and Madina.
Of the copies made by Uthman, two still exist to our day. One is in the city of Tashkent, (Uzbekistan) and the second one is in Istanbul (Turkey). Below is a brief account of both these copies:
1. The copy which Uthman sent to Madina was reportedly removed by the Turkish authorities to Istanbul, from where it came to Berlin during World War I. The Treaty of Versailles, which concluded World War I, contains the following clause:
'Article 246: Within six months from the coming into force of the present Treaty, Germany will restore to His Majesty, King of Hedjaz, the original Koran of Caliph Othman, which was removed from Madina by the Turkish authorities and is stated to have been presented to the ex-Emperor William II".
'This manuscript then reached Istanbul, but not Madina (Where it now resides)'.
2. The second copy in existence is kept in Tashkent, Uzbekistan. 'It may be the Imam (master) manuscript or one of the other copies made at the time of Uthman'.
It Came to Samarkand in 890 Hijra (1485) and remained there till 1868. Then it was taken to St.Petersburg by the Russians in 1869. It remained there till 1917. A Russian orientalist gave a detailed description of it, saying that many pages were damaged and some were missing. A facsimile, some 50 copies, of this mushaf (copy) was produced by S.Pisareff in 1905. A copy was sent to the Ottoman Sultan 'Abdul Hamid, to the Shah of Iran, to the Amir of Bukhara, to Afghanistan, to Fas and some important Muslim personalities. One copy is now in the Columbia University Library (U.S.A.).
'The Manuscript was afterwards returned to its former place and reached Tashkent in 1924, where it has remained since'.
Uthman's version was written in an older Arabic script that left out most vowel markings; thus the script could be interpreted and read in various ways. This basic Uthmanic script is called the rasm; it is the basis of several traditions of oral recitation, differing in minor points. In order to fix these oral recitations and prevent any mistakes, scribes and scholars began annotating the Uthmanic rasm with various diacritical marks indicating how the word was to be pronounced. It is believed that this process of annotation began around 700 CE, soon after Uthman's compilation, and finished by approximately 900 CE.
http://en.wikipedia.org/wiki/Origin_and_development_of_the_Qur'an
PS Memorising the Quran is not an ancient art. I have a cousin who is a Qurra. All imams who conduct prayers in big mosques are Qurras.
They recite the whole Quran during prayers in Ramadan. one juz per day for 30 days.
I forgot about the different scripts:
Today, it is widely believed that Arabic script is a descendent of the Nabataean script. Apart from the Nemara and a few other inscriptions, the earliest surviving document of written Arabic is the Quran, Islam's sacred book revealed to the Prophet Mohammed in the early 7th century A.D. Early Arabic script employed to record the Quran shares several characteristics with the Nemara script such as the use of symbols which hold resemblance in their shapes to denote distinct letters, as in the case of the letters b, t, and th. With the development of the Arabic writing system, more subtleties and refinements were added. During the first year in the Islamic calendar, dots above or below letters were systematically used to differentiate between letters which were identical without the dots. Thus the letters b, t, and th were marked with one dot below (b), two dots above(t), and three dots above (th). And it was not until the early 8th century A.D. that the use of diacritical marks was introduced to secure the correct reading of the Quran. The diacritical system (probably borrowed from the Syriac script) employed short vowels, marked by symbols placed above or below the consonant which they follow in speech. Other symbols placed above the letter marked the absence of a following vowel (sukun), and others, the endings in the inflection of nouns and the moods of verbs. But these marks never came into general use, and to the present day, the system is used mainly in text of the Quran and for teaching purposes.