  We determine the masses and decay constants of pseudoscalar mesons $ D $, $
D_s $, and $ K $ in quenched lattice QCD with exact chiral symmetry. For 100
gauge configurations generated with single-plaquette action at $ \beta = 6.1 $
on the $ 20^3 \times 40 $ lattice, we compute point-to-point quark propagators
for 30 quark masses in the range $ 0.03 \le m_q a \le 0.80 $, and measure the
time-correlation functions of pseudoscalar and vector mesons. The inverse
lattice spacing $ a^{-1} $ is determined with the experimental input of $ f_\pi
$, while the strange quark bare mass $ m_s a = 0.08 $, and the charm quark bare
mass $ m_c a = 0.80 $ are fixed such that the masses of the corresponding
vector mesons are in good agreement with $ \phi(1020) $ and $ J/\psi(3097) $
respectively. Our results of pseudoscalar-meson decay constants are $ f_K =
152(6)(10) $ MeV, $ f_D = 235(8)(14)$ MeV, and $ f_{D_s} = 266(10)(18) $ MeV.
