Peshawar was founded on the Gandhara plains in the broad Valley of Peshawar. The city likely first existed as a small village in the 5th century BCE, within the cultural sphere of eastern ancient Persia. Peshawar was founded near the ancient Gandharan capital city of Pushkalavati, near present-day Charsadda. 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.