The CMKIN code on KINE module offers a standard way to interface kinematics generators like Pythia, Isajet and Herwig with GEANT in CMSIM. This is based on a common block HEPEVT - a HEP standard to store particle kinematics information for one event. For each generator a set of routines, some of which are found from the STDHEP package, is used to convert from generator internal event structure to HEPEVT common. The HEPEVT common is converted to HBOOK ntuples for i/o.
In CMSIM side, in turn, the events are read by CKNTUP (in cmsi module) and put to HEPEVT common from which the routine CKHEPG converts the particle kinematics information to GEANT KINE and VERT structures.
The user controls the i/o file names by CFIL keywords 'EVTO' (output file in CMKIN) and EVSI (input file for CMSIM). At present the interface is available for the three generators mentioned above.