Atlas computes the resulting moments and reaction forces for a given beam with loads applied to it (single as well as distributed), using Cross' method.
A typical application would be to optimize joint positions (i.e. positions with zero moment) in purlins or beams.
The program has a very easy interface. It lets you enter your data with the mouse, and it shows the resulting moments and shear forces immediately in both a graphical and numerical way. Maximum bending moments can easily be calculated.