[en] 1 - Description of program or function: The main purpose of the DIFBAS code is to unfold pulse height spectra measured by a proton recoil detector (e.g. H filled proportional counters or organic scintillators) to obtain neutron spectra. It can be used generally for the unfolding of arbitrary many channel spectra containing original particle spectra folded by a detector response (e.g. spectra of photon detectors). 2 - Method of solution: The algorithm is based on the Bayesian conditional probability assuming normal distributions of both the pulse height and the a priori spectra. The covariance filter method, which avoids any matrix inversion, is employed to calculate the a-posteriori spectrum and covariance matrix of the neutron spectrum