ESDU 79020 gives curves of displacement thickness@ shape parameter and total thickness of the boundary layer using results from a computation method that allows interactively for the displacement effect of the boundary layer and wake. An estimate of accuracy is made using limited experimental data from the literature. The curves are plotted to show the effects of various geometry and flow changes on the boundary layer characteristics: forebody length and shape@ afterbody length and shape@ fineness ratio@ Reynolds number@ Mach number and transition position. ESDU 78019 and 78037 respectively give results computed with the same program for the profile drag and velocity distribution for the same families of bodies made up of a forebody@ afterbody and a cylindrical central portion.