eXplain is a robust tool developed by PKS Software GmbH for code analysis and the assessment of legacy systems, specifically aimed at performing in-depth evaluations of legacy applications on mainframe platforms like IBM i (AS/400) and IBM Z. This software allows organizations to gain insights into their software's contents, structural integrity, and identifies components that may be retained, improved, or phased out. By importing existing source code into a standalone "eXplain server," the tool eliminates the necessity for installations on the host system, utilizing sophisticated parsers to scrutinize programming languages such as COBOL, PL/I, Assembler, Natural, RPG, and JCL, along with information pertaining to databases like Db2, Adabas, and IMS, as well as job schedulers and transaction monitors. eXplain creates a centralized repository that functions as a knowledge hub, from which it can produce cross-language dependency graphs, data-flow diagrams, interface evaluations, groupings of related modules, and comprehensive reports on object and resource usage. This enables users to visualize relationships within the code, enhancing their understanding of the software landscape. Ultimately, eXplain empowers organizations to make informed decisions regarding the future of their legacy systems.