complexity" of ancient India without a writing system for Sanskrit and other languages. The oldest datable writing systems for Sanskrit are the Brāhmī script, the related Kharoṣṭhī script and the Brahmi derivatives. The Kharosthi was used in the northwestern part of South Asia and it became extinct, while the Brahmi was used all over the subcontinent along with regional scripts such as Old Tamil. Of these, the earliest records in the Sanskrit language are in Brahmi, a script that later evolved into numerous related Indic scripts for Sanskrit, along with Southeast Asian scripts (Burmese, Thai, Lao, Khmer, others) and many extinct Central Asian scripts such as those discovered along with the Kharosthi in the Tarim Basin of western China and in Uzbekistan. The most extensive inscriptions that have survived into the modern era are the rock edicts and pillar inscriptions of the 3rd century BCE Mauryan emperor Ashoka, but these are not in Sanskrit. Scripts Over the centuries, and across countries, a number of scripts have been used to write Sanskrit. Brahmi script The Brahmi script for writing Sanskrit is a "modified consonant-syllabic" script. The graphic syllable is its basic unit, and this consists of a consonant with or without diacritic modifications. Since the vowel is an integral part of the consonants, and given the efficiently compacted, fused consonant cluster morphology for Sanskrit words and grammar, the Brahmi and its derivative writing systems deploy ligatures, diacritics and relative positioning of the vowel to inform the reader how the vowel is related to the consonant and how it is expected to be pronounced for clarity. This feature of Brahmi and its modern Indic script derivatives makes it difficult to classify it under the main script types used for the writing systems for most of the world's languages, namely logographic, syllabic and alphabetic. The Brahmi script evolved into "a vast number of forms and derivatives", states Richard Salomon, and in theory, Sanskrit "can be represented in virtually any of the main Brahmi-based scripts and in practice it often is". From the ancient times, it has been written in numerous regional scripts in South and Southeast Asia. Most of these are descendants of the Brahmi script. The earliest datable varnamala Brahmi alphabet system, found in later Sanskrit texts, is from the 2nd century BCE, in the form of a terracotta plaque found in Sughana, Haryana. It shows a "schoolboy's writing lessons", states Salomon.