Wikipedia
The Tolkāppiyam is a work on the grammar of the Tamil language and the earliest extant work of Tamil literature and linguistics. It is written in the form of noorpaa or short formulaic compositions and comprises three books – the Ezhuttadikaram, the Solladikaram and the Poruladikaram. Each of these books is further divided into nine chapters each. While the exact date of the work is not known, based on linguistic and other evidence, it has been dated variously between the third century BCE and the 10th century CE. Some modern scholars prefer to date it not as a single entity but in parts or layers. There is also no firm evidence to assign the authorship of this treatise to any one author.
Tolkappiyam deals with orthography, phonology, morphology, semantics, prosody and the subject matter of literature. The Tolkāppiyam classifies the Tamil language into sentamil and koduntamil. The former refers to the classical Tamil used almost exclusively in literary works and the latter refers to the dialectal Tamil, spoken by the people in the various @ regions of ancient Tamilagam.
Tolkappiyam categorises alphabet into consonants and vowels by analysing the syllables. It grammatises the use of words and syntaxes and moves into higher modes of language analysis. The Tolkāppiyam formulated thirty phonemes and three dependent sounds for Tamil.