Tally Definition Language (TDL) is the development language of Tally.ERP 9. TDL is developed to provide the user with the flexibility and power to extend the default capabilities of Tally, and integrate them with the external applications. TDL provides a development platform for the user. The entire user interface of Tally.ERP 9 is built using TDL. TDL as a language, provides capabilities for Rapid Development, Rendering, Data Management, and Integration.