The density of states, DoS, is the spectrum of the number of energy levels per eV versus energy. While the energy levels resulting from the calculation of the band structure could be used directly for the calculation of the DoS, the resulting DoS would be very rough as a result of the relatively coarse mesh used. A better procedure is to assume continuity of the bands, and, by using an interpolation procedure, numerically integrate. A possible complication arises from the incorrect representation of bands which should cross. In practice, however, errors due to such causes are so small as to not show up in a normal graphical representation of the DoS.
At present, the DoS is not calculated in MOPAC.