Was going to point out would have to be an embedded program that can be booted into without need of an OS; but then program would still rely on various external

Was going to point out would have to be an embedded program that can be booted into without need of an OS; but then program would still rely on various external api/abi interfaces aka bios, drivers & protocols (usb, scsi, pci, ansi, etc). Given today's hardware, think there's not really a realizstic thing as a realistic reall world 'pure C' program -- way to much knowledge / effort even if exclude NDA's. VM environment for 'hardware' as software still has abi interface, so not 'pure' C at source code level.