Development of the original NEC codes continued at LLNL, producing NEC-3 which added the ability to model elements buried in or projecting out of the ground, and NEC-4, which included a wide variety of updates. NEC-4 formalized what was already widely the case, taking input from a specified file, sending output to another file, and allowing comments to be added to any line using the codice_1 character. NEC-4 also introduced a new licensing system, and is not available as open source.