  In this article we have illustrated how is possible to formulate Maxwell's
equations in vacuum in an independent form of the usual systems of units.
Maxwell's equations, are then specialized to the most commonly used systems of
units: International system of units (SI), Gaussian normal, Gaussian rational
(Heaviside-Lorentz), C.G.S. (electric), C.G.S. (magnetic), natural normal and
natural rational. Both, the differential and the integral formulations of
Maxwell's equations in vacuum, are illustrated. Also the covariant formulation
of Maxwell's equation is illustrated.
