plus4emu is a portable, open source emulator of the Commodore Plus/4 plus4emu is a portable, open source emulator of the Commodore Plus/4 computer. plus4emu is written in C++, and supporting Windows and POSIX platforms (32 bit Windows, 32 and 64 bit Linux, and MacOS X have been tested). plus4emu implements accurate, high quality hardware emulation, however, the system requirements are higher than that of most other emulators.