  We present BIGSTICK, a flexible configuration-interaction open-source
shell-model code for the many-fermion problem. Written mostly in Fortran 90
with some later extensions, BIGSTICK utilizes a factorized on-the-fly algorithm
for computing many-body matrix elements, and has both MPI (distributed memory)
and OpenMP (shared memory) parallelization, and can run on platforms ranging
from laptops to the largest parallel supercomputers. It uses a flexible yet
efficient many-body truncation scheme, and reads input files in multiple
formats, allowing one to tackle both phenomenological (major valence shell
space) and ab initio (the so-called no-core shell model) calculations. BIGSTICK
can generate energy spectra, static and transition one-body densities, and
expectation values of scalar operators. Using the built-in Lanczos algorithm
one can compute transition probability distributions and decompose wave
functions into components defined by group theory.
  This manual provides a general guide to compiling and running BIGSTICK, which
comes with numerous sample input files, as well as some of the basic theory
underlying the code.
