[en] 1 - Description of program or function: DDCS is a program for calculating the neutron or charged particles (p, d, t, He³, alpha) induced reactions of medium-heavy nuclei in the incident energy range up to 50 MeV including 5 emission processes. For those reaction channels contributed only by 1-4 emission processes the incident energy can go up to 100 MeV. The double differential cross sections, various cross sections, and spectra can be calculated in this program. DDCS is constructed within the framework of the optical model, generalized master equation of the exciton model, and the evaporation model. In the first and second particle emission processes, we consider pre-equilibrium emission and evaporation; in 3-5 particle emission processes, we only consider evaporation. The pre-equilibrium and direct reaction mechanisms of gamma emission are also included in this program. The effect of recoil nucleus is taken into account. Program DDCS includes the first to the fifth particle emission processes. a+A → b+B*, a=n, p, alpha, d, t, He³, b=n, p, alpha, d, t, He³, gamma; B* → c+C*, c=n, p, alpha, d, t, He³, gamma; C* → d+D*, d=n, p, alpha, d, t, He³, gamma; D* → d+E*, e=n, p, alpha, d, gamma; E* → f+F*, f=n, p, gamma. When a particle is emitted, the residual nucleus may emit another particle or gamma ray continuously if the excited energy is large enough to overcome the binding energy. Generally speaking, the gamma emission cross section is much less than neutron emission cross section when the neutron emission channel is opened. We assume that after gamma ray is emitted the residual nucleus does not emit any particle except that after the first gamma ray emission process the particle or gamma are allowed to be emitted. Thus, 7 channels can be opened for the first emission process, 49 channels for the second emission process 252 channels for third emission process, 1080 channels for forth emission process, and 2592 channels for firth-emission process. The following nuclear data can be calculated with the program DDCS: the double differential emission cross sections of emitted nucleons (n and p) and composite particle (alpha, d, t, He³) in laboratory or C. M. system, as well as total emission cross sections and spectra of all emitted particles; the partial emission cross sections and spectra of all emitted particles for first to sixth particle emission processes and pick-up configurations (1,m) and (2,m); the various yield cross sections; total and elastic scattering cross sections (only for neutron as projectile); total reaction cross section; nonelastic scattering cross sections; radiative capture cross section; (x, np), (x,n alpha), (x,2n), (x,3n), (x,4n), (x,5n) cross sections and so on. 2 - Method of solution: The Gilbert-Cameron level density formula was applied in program DDCS. The inverse cross sections of the emitted particles used in statistical theory are calculated from the optical model. The partial widths for gamma-ray emission are calculated based on the giant dipole resonance model with two resonance peaks in both the evaporation model and exciton model. In the optical model calculation, we usually adopt the Becchetti and Greenlee's phenomenological optical potential, which parameters are usually given by a program for automatically searching the optimum optical model parameters. We use Neumanove methods to solve the radial equation in optical model. Coulomb wave functions used in optical model are calculated by the continued fraction method. DDCS does not calculate the direct inelastic scattering and compound nucleus elastic scattering data, but the calculated direct inelastic scattering cross sections and angular distributions by the collective excitation distorted-wave Born approximation and compound nucleus elastic scattering cross sections and elastic scattering angular distributions by Hauser-Feshbach model and optical model can be added in the input data of the program DDCS. 3 - Restrictions on the complexity of the problem: 1) The calculations are restricted to medium-heavy nucl ei, for which fission reactions are absent. 2) The incident particle is restricted to n(neutron), p(proton), d(deuteron), alpha(helium-4), t(triton), and He³(helium-3). The outgoing particles only include n(neutron) and the above 5 charged particles as well as gamma photons