Data structures are schemes that organize data to permit efficient access in certain modes. The desired modes of access (different kinds of look-ups and modifications), and their relative importance in an application, typically guide the choice of existing data structures and the design of new ones. A judicious choice of data structures often results in very significant improvements in the running time of a program. In order to make such decisions, as well as to design new data structures, we need to understand existing data structures, their access modes, and performance characteristics. In this course, we study data structures from several perspectives, including design, analysis, and application.