This computer code (written in C language) determines the internal constitution of the outer crust of a cold nonaccreted magnetar using the very fast iterative analytical method originally presented in Phys. Rev. C 101, 032801(R) (2020) for unmagnetized neutron stars (for which a computer code is also available here). The effects of the strong magnetic field are taken into account through the Landau-Rabi quantization of the electron motion assuming that only the first level is filled. Further details can be found in Phys. Rev. C 101, 065802 (2020) Instead of performing the full numerical minimization of the Gibbs free energy per nucleon for each pressure as in the traditional approach, the sequence of equilibrium nuclei is found by making use of very accurate analytical formulas for the transition pressures between adjacent crustal layers and their density. In addition to the composition of the different crustal layers, their proper depth and their baryonic mass are simultaneously estimated using an approximate solution of Einstein's general relativistic equations. An example file containing data from the 2016 Atomic Mass Evaluation, measurements of copper isotopes, and from the theoretical nuclear mass model HFB-27 can be found here. Usage: smagcrust atomic_mass_data_file [options] Options: -w Wigner-Seitz approximation. The format of atomic_mass_data_file should be the following: atomic number / mass number / mass excess in MeV Help: smagcrust -h

This work was financially supported by Fonds de la Recherche Scientifique - FNRS (Belgium) under grant No. IISN 4.4502.19 and by the National programme "Young scientists" funded by the Bulgarian Ministry of Education and Science.

{"references": ["Chamel, Phys. Rev. C 101, 032801(R) (2020)", "Chamel&Stoyanov, Phys. Rev. C 101, 065802 (2020)"]}