Hercules is a computer emulator allowing software written for IBM mainframe computers (System/370, System/390, and zSeries/System z) and for plug compatible mainframes (such as Amdahl machines) to run on other types of computer hardware, notably on low-cost personal computers.Although there are other mainframe emulators performing a similar function, Hercules is significant in enabling private individuals to run mainframe computer software on their own personal computers.Hercules runs under multiple parent operating systems including Linux, MS Windows, FreeBSD, Oracle Solaris, and Apple Mac OS X and is released under the open source software license QPL.