Arnold is an Amstrad CPC/CPC+/GX4000 emulator. It can also emulate the KC Compact, a bootleg CPC clone.
Arnold was originally written by Kevin Thacker. The MacOS port was developed by Richard Bannister. The documentation was written by Jacques Azoulai, with updates and minor tweaks by Richard Bannister. The icons were designed as a special favour to me by PB1400c - thank you very much indeed!
When the CPC was originally developed, the code name of Arnold was used. This is where the name of the emulator comes from.