MOLCAS manual: 6. Program Based Tutorials The MOLCAS 8.1 suite of Quantum Chemical programs is modular in design. The desired calculation is achieved by executing a list of MOLCAS program modules in succession, while potentially manipulating the program information files. If the information files from a previous calculation are saved, then a subsequent calculation need not recompute them. This is dependent on the correct information being preserved in the information files for subsequent calculations. Each module has keywords to specify the functions to be carried out, and many modules rely on the specification of keywords in previous modules. The following sections describe the use of the MOLCAS modules and their inter-relationships. Each module is introduced in the approximate order for performing a typical calculation. A complete flowchart for the MOLCAS 8.1 suite of programs follows.