The Sahabas (may Allah's blessings be upon them all) gave special care to the holly Quran as they are the first generation and the pioneers in transferring to us the great Book of Allah the Almighty; because they realized the grace of the Book; they loved it with whole-heartedness, and their feelings were overwhelmed by the affection of the Quran.
A group of Sahabas were known as the best reciters such Abdullah ibn Masu’d, Ubai ibn Ka’ab and Zaid ibn Thabit (may Allah's blessings be upon him). Others used to collect wood by daytime and learn to recite Quran at night, so they named the reciters “Qurra’”. Sahabas also used to combine between memorizing as well as understanding and applying the Quran. Ibn Masu’d (may Allah's blessings be upon him) said: “We used to repeat only 10 verses till we know their exact meanings and apply them”.
This is the method they used to memorize and learn the Qur'an, and therefore it took them ages to memorize the holly Quran. It was narrated that Ibn Omer (may Allah's blessings be upon him) spent eight years to memorize surah Al-Baqara.
One sign for their special care of the Quran is that they probably used to learn it in turns from the prophet as they were living in a distance from the location of the Prophet (PBUH). For example if a day Omer arrived to learn the revelation, the other day would be Alansari’s turn, and when they came back home, they taught each other.
Another sign of the Sahabas (may Allah's blessings be upon them all) care of the Quran, they were learning the rules of punctuations such as Waqf (Stopping) and Ibtida (start) relating to places where they should pause and some places where they should not break their words.
Sahabas were also extremely careful about words formation and pronunciation and that was the beginning of transferring the science of all styles of recitations (qira’at), the rules of recitation (Tajweed) are embedded in the transfer of qira’at. Thus Tajweed is the infrastructure or basic rule of qira’at. In this way Sahabas learned the principles of recitation, in addition to their Arabic tongue. In other words, some rules of recitation were known to them by default as they naturally mastered the Arabic language. However, there are some topics of recitations need to be learned by rote, and therefore Sahabas also had to consolidate these topics, applications and qualities. And through this method, they were able to transfer them honestly and enthusiastically to the next generations.