In this paper, implementation concepts of a structural optimization software using object-oriented programming (OOP) in CS ++ is presented. A brief mathematical formulation of structural optimization and continuum-based sensitivity analysis is presented. The requirements of a computational optimization environment are derived from this formulation. The OOP characteristics are analysed and this paradigm is employed in the implementation of design variables, structural performance functionals, velocity fields, design model and mathematical programming algorithms using CI-Jr. Finally, the program obtained is applied to 2D linear elastic examples of sizing and shape optimization.202154166