Even null in programming languages isn't so bad if it's a distinct type. The problem with null in languages like Java is that null is part of every reference type (C's pointers are another world of broken, null being basically just another unsafe invalid address).
Most languages nowadays do get nulls right, even PHP of all things.
Ironically NULL is probably the safest pointer value in C, as any dereferences from it (and thousands of pages that follow it) are guaranteed to crash.
Well, that's a problem on many of the devices I've seen: zero is a valid memory address and dereferencing it does not cause any kind of crash. In fact some hardware requires reading or maybe even writing to that address. In an age of virtual memory there's no reason why zero should cause a crash and it wastes an entire page of memory for every application to make that happen, if it does.
I haven't had the chance to work on any MMU-less devices, but I don't quite follow your remark about wasting a page. Crashing is just the default behaviour in the absence of a mapping and consumes no resources.
The granularity of virtual address mapping is usually a page. On many systems, that's 4 kilobytes of address space. In order to trigger a fault when the address 0x0000000000000000 is dereferenced, it's necessary to map the entire address range from 0x0000000000000000 to 0x0000000000000fff to the same faulting behaviour.
Yeah but there is no "page" there. Assuming a process starts with an empty page table (meaning every single address will segfault), you don't have to do anything else to get the crashing behaviour for null.
Unless you're talking about some kind of device which supports virtual memory, but also by default sets up mappings, including at 0 which seems weird to me.
Most languages nowadays do get nulls right, even PHP of all things.