The numerical study of the divers magnetic field configurations in the Novillo Tokamak developed by means of the CAMTOK code is presented to illustrate not only the application of classical analysis to a specific case but also a straightforward technique to develop magnetic design codes. Algorithms and results in the case of the ohmic heating transformer, toroidal, and equilibrium systems are presented. On the basis of CAMTOK simulations and measured values, stray components of the fields are identified and suppressed, leading to the redesign of the original concept of the Novillo tokamak into its current operating configuration.