Free42 is a complete re-implementation of the HP-42S calculator and the HP-82240 printer. It was written from scratch, without using any HP code. You do not need any ROM images in order to use it, yet it is fully HP-42S compatible.

Free42 is an Open Source project; the executables and source code are released under the terms of the GNU General Public License, version 2. All third-party code used in Free42 is either in the public domain, or licensed under terms compatible with GPLv2, or used with permission of the respective authors.