[en] We present the computer program DeCE developed at Los Alamos National Laboratory, which is open-source software to assist in producing evaluated nuclear data files. DeCE manipulates a provided evaluated nuclear data file interactively, then creates a new file in an ENDF-6 legitimate format. DeCE also extracts numerical data given in an evaluated file and converts into a more readable format. The code includes two C++ libraries, ENDFLIB and ENDFIO, which fulfill a demand for easy interface between a modern computer programming technique and the inflexible ENDF-6 format. We overview the DeCE code and the libraries employed there, and demonstrate their capabilities. (author)