Also the C null pointer on modern system is the logical (virtual memory) address which is not necessarily mapped to 0x0 physical address - in fact, to trap the null pointer access, this page would be left unmapped so the OS receives a page fault. This means that before virtual memory is set up (or if a page is mapped for logical address 0x0), 0x0 is a perfectly valid memory location, both for data storage and executing instructions from. Basically, the null pointer "error" is trapped by the OS at a higher level.