DOCK 6 is written in C++, and is functionally divided into independent components, thus having a high degree of program flexibility. The attached program is written in C and Fortran 77. The workflow of DOCK6 is shown in the figure. The first is to prepare according to the geometric coordinates of the receptor and the ligand, and then do docking. There are three processes for receptor preparation: Sphgen, Grid and DOCK. The process is shown in Figure 2. The Sphgen process identifies the corresponding site and generates the center of the sphere that can fill the site. The Grid process generates a scoring grid. In the program DOCK, DOCK matches spheres (generated by Sphgen) with ligand atoms and uses a scoring grid (from Grid) to evaluate the orientation of the ligand. Program docking can also minimize energy-based scores.