Forget on-disk. Different CPUs represent basic data types with different in-memory representations (endianness). Furthermore different CPUs have different capabilities with respect to how data must be aligned in memory in order to read or write it (aligned/unaligned access). At least historically unaligned access could fault your process. Then there's the problem, that you allude to, that different programming languages use different data layouts (or often a non-standardised layout). If you want communication within a system comprising heterogeneous CPUs and/or languages, you need to translate or standardise your a wire format and/or provide a translation layer aka serialisation.