sentence: ( os from microware for intel x86 based microcomputers ; based on os-9 , written in c ) osf/1 ( developed into a commercial offering by digital equipment corporation ) openstep qnx ( posix , microkernel os ; usually a real time embedded os ) rhapsody ( an early form of os x ) risc ix - derived from bsd 4.3 , by acorn computers , for their arm family of machines .