  Using the large hadroproduced charm sample collected in experiment E791 at
Fermilab, we have measured ratios of branching fractions for the two-body
singly-Cabibbo-suppressed charged decays of the D0:
  (D0 -> KK)/(D0 -> Kpi) = 0.109 +- 0.003 +- 0.003,
  (D0 -> pipi)/(D0 -> Kpi) = 0.040 +- 0.002 +- 0.003, and
  (D0 -> KK)/(D0 -> pipi) = 2.75 +- 0.15 +- 0.16. We have looked for
differences in the decay rates of D0 and D0bar to the CP eigenstates K+K- and
pi+pi-, and have measured the CP asymmetry parameters
  A_CP(K+K-) = -0.010 +- 0.049 +- 0.012 and
  A_CP(pi+pi-) = -0.049 +- 0.078 +- 0.030, both consistent with zero.
