  Let G be a connected reductive group over the field of real numbers R. Using
results of our previous joint paper, we compute combinatorially the first
Galois cohomology set H^1(R,G) in terms of reductive Kac labelings. Moreover,
we compute the group of connected components \pi_0 G(R) of the real Lie group
G(R) and the maps in exact sequences containing \pi_0 G(R) and H^1(R,G).
