The Arduino IDE calls out to avr-gcc, and mbed-os is written in c++ so requires an embedded c++ compiler like arm-gcc or something similar. ChromeOS also runs t

The Arduino IDE calls out to avr-gcc, and mbed-os is written in c++ so requires an embedded c++ compiler like arm-gcc or something similar. ChromeOS also runs the Linux kernel so you do need it to compile the OS, and it can hypothetically run binaries compiled for the linux platform. Dig deep enough through all the layers of bootstrapping and you'll find c basically everywhere.