This paper concerns creation of libraries of reusable objects in the language C++for doing accelerator design and analysis. The C++language possesses features which lend themselves to writing portable, scientific solftware. The two libraries of C++classes (objects) which have been under development are (1) MXYZPTLK, which implements automatic differentiation and (2) BEAMLINE, which provides objects for modeling beam line and accelerator components. A description of the principle classes in these two libraries is presented. (AIP)