Vedas came down generations by oral teaching from the teachers or father’s mouth to the student or the son. The Vedic people had known no art of writing.
Vedic Brahmi Script:
The Brahmi script is a script evolved by the Vedic philologists after an inspection of sources of sound from Ganesh Vidhya and the causes of variations of sound. Brahmi was distinct and superior to all other scripts, perfect in phonetic arrangement and nasal signs. Each sign can be either a simple consonant or the inherent vowel. Brahmi (and all subsequent Brahmi-derived scripts) indicates the same consonant with a different vowel by drawing extra strokes, called matras, attached to the character. Ligatures are used to indicate consonant clusters.
The Brahmi continued to spread during Buddhist and Jaina though the Aa kaar was not present. But it became a permanent feature in the Bhagwat Gita which is called as ‘Bharati Script’. The Bharati script began to evolve in Gupta period (4 to 6 century A.D.). The transition can be seen from the Brahmi script to the Bharati script to the Gupta script to Nagari script to Devanagari.