  We show that the low-energy fluctuations of the valence bond in underdoped
high-T_c cuprates, originating from quantum fluctuations of the superexchange
interaction, are pinned by the electronic disorder due to off-stoichiometric
dopants, leading to a valence bond glass (VBG) pseudogap phase. The antinodal
Fermi surface sections are gapped out, giving rise to a normal state Fermi arc
whose length shrinks with underdoping. Below T_c, the superexchange interaction
induces a d-wave superconducting gap that coexists with the VBG pseudogap. The
evolution of the local and momentum-space spectroscopy with doping and
temperature captures the salient properties of the pseudogap phenomena and the
electronic disorder. The unified theory elucidates the important interplay
between strong correlation and the intrinsic electronic disorder in doped
transition metal oxides.
