 Peshawar is the city in which fourth century B.C.E Philologist Pāṇini wrote the book 'Aṣṭādhyāyī' on Sanskrit Grammar which became the basis for structural linguistics used in modern languages and the formal system used in computer programming languages.In the winter of 327–26 BCE, Alexander the Great subdued the Valley of Peshawar during his invasion of ancient India, as well as the nearby Swat and Buner valleys.Following Alexander's conquest, the Valley of Peshawar came under suzerainty of Seleucus I Nicator, founder of the Seleucid Empire.