which have borrowed Sanskrit terms such as bahuvrihi and dvandva.Panini's comprehensive and scientific theory of grammar is conventionally taken to mark the end of the period of Vedic Sanskrit, so by definition introducing Classical Sanskrit.

though it is generally agreed that he knew of a form of writing, based on references to words such as "script" and "scribe" in his Ashtadhyayi. These must have referred to Aramaic or early Kharosthi writing. It is believed by some that a work of such complexity would have been difficult to compile without written notes, though others have argued that he might have composed it with the help of a group of students whose memories served him as 'notepads' (as is typical in Vedic learning).

Writing first reappears in India in the form of the Brahmi script from c. the 3rd century BC in the Ashokan inscriptions.

While Panini's work is purely grammatical and lexicographic, cultural and geographical inferences can be drawn from the vocabulary he uses in examples, and from his references to fellow grammarians, which show he was a northwestern person. New deities referred to in his work include Vasudeva (4.3.98). The concept of dharma is attested in his example sentence (4.4.41) dharmam carati "he observes the law" (cf. Taittiriya Upanishad 1.11).

Nothing certain is known about Panini's personal life. According to later traditions, his mother's name was Daksi and his maternal uncle's name was Vyadi. Some scholars suggest that his brother's name was Pingala. Still less is known about his father, whose name may have been Paṇi, but most scholars reject this suggestion. More than a thousand years after the fact, the Panchatantra mentions that the Grammarian Panini was killed by a lion.

The Ashtadhyayi is the central part of Panini's grammar, and by far the most complex. It is the earliest complete grammar of Classical Sanskrit, and in fact is of a brevity and completeness unmatched in any ancient grammar of any language. It takes material from the lexical lists (Dhatupatha, Ganapatha) as input and describes algorithms to be applied to them for the generation of well-formed words. It is highly systematised and technical. Inherent in its approach are the concepts of the phoneme, the morpheme and the root. His rules have a reputation for perfection -

that is, they are claimed to describe Sanskrit morphology fully, without any redundancy. A consequence of his grammar's focus on brevity is its highly unintuitive structure, reminiscent of modern notations such as the "Backus–Naur Form". His sophisticated logical rules and technique have been widely influential in ancient and modern linguistics.

It is likely that Panini's grammar and the Rg Veda are the only texts that were passed from one generation to another without being amended. In the Ashtadhyayi language is observed in a manner that has no parallel among Greek or Latin grammarians.

Panini's grammar marks the entry of the non-sacred into Indian thought, and according to Renou and Filliozat, it then defines the linguistic expression of that thought.

The great thinkers of ancient India were primarily linguists. It is not possible to understand fully the works of theologians/philosophers such as Shankara, Ramanuja and Madhva without a knowledge of Panini.The Ashtadhyayi is fundamental to the structure of their thinking. It is not a didactic grammar, as it presupposes a knowledge of Sanskrit.

Gradually,mainly after the X century, manuals were produced that reorganised the Ashtadhyayi for didactic purposes.

These generally had simpler structures and were less ambitious than their Ashtadhyayi source.

Panini made use of a technical metalanguage consisting of a syntax, morphology and lexicon. This metalanguage is organised according to a series of meta-rules, some of which are explicitly stated while others can be deduced. The fundamental principles on which the metalanguage is based are non-redundancy,or the principle of economy,and the necessity of all the rules in the Ashtadhyayi.

The Ashtadhyayi consists of 3,959 sutras (Sutrani) or rules, distributed among eight chapters, which are each subdivided into four sections or padas (padah).

From example words in the text, and from a few rules depending on the context of the discourse, additional information as to the geographical, cultural and historical context of Panini can be discerned.

You can find some of the Rules in the link attached above with article.

Pāṇini's Ashtadhyayi has three associated texts.

The Shiva Sutras are a brief but highly organized list of phonemes.

 The Dhatupatha is a lexical list of verbal roots sorted by present class.

The Ganapatha is a lexical list of nominal stems grouped by common properties.

The Shiva Sutras describe a phonemic notational system in the fourteen initial lines preceding the Ashtadhyayi. The notational system introduces different clusters of phonemes that serve special roles in the morphology of Sanskrit, and are referred to throughout the text. Each cluster, called a pratyāhara ends with a dummy sound called an anubandha (the so calledIT index), which acts as a symbolic referent for the list. Within the main text, these clusters, referred through the anubandhas, are related to various grammatical functions.

The Dhatupatha is a lexicon of Sanskrit verbal roots subservient to the Ashtadhyayi. It is organized by the ten present classes of Sanskrit, i.e. the roots are grouped by the form of their stem in the present tense.

The ten present classes of Sanskrit are:

    1. bhū-ādayaḥ (root-full grade thematic presents)

    2. ad-ādayaḥ (root presents)

    3. ju-ho-ti-ādayaḥ (reduplicated presents)

    4. div-ādayaḥ (ya thematic presents)

    5. su-ādayaḥ (nu presents)

    6. tud-ādayaḥ (root-zero grade thematic presents)

    7. rudh-ādayaḥ (n-infix presents)

    8. tan-ādayaḥ (no presents)

 9. krī-ādayaḥ (ni presents)

10. cur-ādayaḥ (aya presents, causatives)

Most of these classes are directly inherited from Proto-Indo-European. The small number of class 8 verbs are a secondary group derived from class 5 roots, and class 10 is a special case, in that any verb can form class 10 presents, then assuming causative meaning. The roots specifically listed as belonging to class 10 are those for which any other form has fallen out of use (causative deponents, so to speak).

The Ganapatha (gaṇapāṭha) is a list of groups of primitive nominal stems used by the Ashtadhyayi.

After Pāṇini, the Mahābhāṣya ("great commentary") of Patañjali on the Ashtadhyayi is one of the three most famous works in Sanskrit grammar. It was with Patañjali that Indian linguistic science reached its definite form. The system thus established is extremely detailed as to shiksha (phonology, including accent) and vyakaran(morphology). Syntax is scarcely touched,but nirukta (etymology) is discussed, and these etymologies naturally lead to semantic explanations.

The learning of Indian curriculum in late classical times had at its heart a system of grammatical study and linguistic analysis. The core text for this study was the Aṣṭādhyāyī of Pāṇini, the sine qua non of learning. This grammar of Pāṇini had been the object of intense study for the ten centuries prior to the composition of the Bhaṭṭikāvya. It was plainly Bhaṭṭi’s purpose to provide a study aid to Pāṇini’s text by using the examples already provided in the existing grammatical commentaries in the context of the gripping and morally improving story of the Rāmāyaṇa.

To the dry bones of this grammar Bhaṭṭi has given juicy flesh in his poem. The intention of the author was to teach this advanced science through a relatively easy and pleasant medium. In his own words:

This composition is like a lamp to those who perceive the meaning of words and like a hand mirror for a blind man to those without grammar. This poem, which is to be understood by means of a commentary, is a joy to those sufficiently learned: through my fondness for the scholar I have here slighted the dullard.Bhaṭṭikāvya 22.33–34.

General purpose high-level programming language such as C++ or Python. This includes object-oriented concepts of classes, parent/child inheritance or base/derived classes, overriding of inherited methods in derived classes, concept of functions, concept of keywords, etc. Of course, algorithmic derivation of results is a given.

The defining feature of Pāṇini’s Aṣṭādhyāyī sūtras is the use of its own special meta-language to describe the rules of the real language i.e. Sanskrit. Let that thought sink in — a language being defined using a meta-language constructed from the same language!