Using Tally Definition Language (TDL), a person can talk to Tally. It is the development language of Tally.ERP 9. It is a powerful and flexible language that provides users with the ability to extend the default capabilities of Tally ERP 9 and integrate it with external applications.   TDL also provides a development platform for users. It provides capabilities for rapid development, rendering, data management, and integration.   TDL includes definitions, data types, symbols, objects and collections, action and event framework, variables framework, user-defined fields, reports, printing and validation controls, and functions.   With TDL, users can customize vouchers, invoices, and other documents. TDL can also be used to develop custom solutions and integrate them with other applications.