In computational chemistry, NDDO (neglect of diatomic differential overlap) is a formalism that was first introduced by John Pople; it is the basis for most semiempirical methods.
The common software program is MOPAC (Molecular Orbital PACkage).
The two-electron integrals from the NDDO approximation can either be one-, two-, three- or four-centered.
The one- and two-centered integrals are evaluated approximately or parameterized based on the experimental data, while the three- and four-centered integrals vanish.
Semiempirical calculations are usually carried out in a minimal basis set.