As far as i know, they introduce protections of few parts, but from coding side i know only about one (sorry for lame explain) : when you just make in your programm "STATIC const something", or "STATIC blalblab", then all your arrays will be in some kind of "protected memory". And when any programm (include main one , with that array blocks), will try to write by this memory area, will crashes with GR on os4 (what mean that some kind of memory protection happens). On other oses (and that include mos/aros and of course os3), its all just happens in silence, and those areas not protected. I can't remember right now, in which code-segment that static arrays are puts (.rodata, or something), but i remember that "readelf" and "objdump", do not show that this code segment are protected (while in reality is it, just those tools was not updated with os4 changes in that terms). Related to what we can do to make our apps better, its all the time use STATIC consts stuff (to add some "protection" ), and MEMF_VIRTUAL for all the AllocMem (not MEMF_PRIVATE or MEMF_SHARED). With MEMF_VIRTUAL, memory can be swapped, so its some sort of protection as well. Will be intersting to discuss all of this (and maybe make an article which cover all what we have in terms of MP from coder's point of view).