Firmware > OpenFirmware
Open Firmware (also known as OpenBoot) is a hardware-independent firmware (computer software which loads the operating system), developed by Mitch Bradley at Sun Microsystems, and used in post-NuBus PowerPC-based Apple Macintosh computers (though it has been dropped with Apple's transition to Intel processors), Sun Microsystems SPARC based workstations and servers, IBM POWER systems, and PegasosPPC systems, among others. On those computers, Open Firmware fulfills the same tasks as BIOS does on PC computers.
It is accessed by a user by a Forth-based shell interface. Forth is a powerful high level language.
Debian uses the YaBoot boot loader for Open Firmware.