  Despite the tremendous advances made by the ab initio theory of electronic
structure of atoms and molecules, its applications are still not possible for
very large systems. Therefore, semi-empirical model Hamiltonians based on the
zero-differential overlap (ZDO) approach such as the Pariser-Parr-Pople, CNDO,
INDO, etc. provide attractive, and computationally tractable, alternatives to
the ab initio treatment of large systems. In this paper we describe a Fortran
90 computer program developed by us, that uses CNDO/2 and INDO methods to solve
Hartree-Fock(HF) equation for molecular systems. The INDO method can be used
for the molecules containing the first-row atoms, while the CNDO/2 method is
applicable to those containing both the first-, and the second-row, atoms. We
have paid particular attention to computational efficiency while developing the
code, and, therefore, it allows us to perform calculations on large molecules
such as C_60 on small computers within a matter of seconds. Besides being able
to compute the molecular orbitals and total energies, our code is also able to
compute properties such as the electric dipole moment, Mulliken population
analysis, and linear optical absorption spectrum of the system. We also
demonstrate how the program can be used to compute the total energy per unit
cell of a polymer. The applications presented in this paper include small
organic and inorganic molecules, fullerene C_60, and model polymeric systems,
viz., chains containing alternating boron and nitrogen atoms (BN chain), and
carbon atoms (C chain).
