Since the ready packages are expensive and may not be obtained easily, the task of writing a comprehensive software package for lenses and optical systems design is adopted in this work. The suggested name to this package is "CALOSD" which is an acronym for "Computer Aided Lens and Optics! Systems Design". Some of its main features are: i)It is written in QB ASIC computer language with the abilities of graphing, optical systems and visualizing ray traces. ii)It is a user friendly software with "pull down" menus. iii)It is capable of producing graphical displays as well as very accurate tabulated data .This prt ent work is based on four optical treatment methods with sophisticated subroutines written to implement them. These methods are: 1.Meridional Approximated Method (MAM). 2. Meridional Exact Method (MEM). 3.Skew Approximated Method (SAM). 4. Skew Exact Method (SEM). The treatment of meridional rays by MAM and MEM are 2D (two dimensional) ones, while SAM and SEM treat the skew rays in 3D (three dimensional). A new model to perform SAM calculations is suggested in this work. This model considers a spherical lens as if it consists of two perpendicular sets of lengthless cylindrical sublenses. i.e. the suggested method divides the complicated 3D SAM problem into two similar 2D MAM problems. SEM software allows an interactive adjustment of the imafpng plane until a spot diagram of least confusion is obtained The spot diagrams can be used to J detect the presence of aberrations.