... The AST library provides a comprehensive range of facilities for creating and using world coordinate systems that describe astronomical data. This paper gives a brief over-view of these facilities and a description of the integration of these facilities with the Starlink ``Extensible N-Dimensional Data Format'' (NDF), which stores bulk data in the form of N-dimensional arrays of numbers. ... WCS - A new component which provides facilities for storing an AST FrameSet . ... Display of WCS grids . ...