Lapis the Nevrean

but I can. I do it all the time. Works great. Don't try to drag everyone down with you.

x86 has the interrupt vector table at 0000:0000 in real mode and the first entry is the address for the divide by zero CPU exception handler, which is attached by DOS (or whatever OS) to a handler that kills the running program. Couple that with no memory protection, and reading from a null pointer will give you some quasi-random values that are essentially static at runtime. Even better, writing to it not only works fine but until and unless a program actually triggers a divide-by-zero, it will continue to work fine and you can read back what was written, no problem. The upshot of this is that for small values (anything smaller than 32-bits) you can read and write to a null pointer's target just fine and you'll never notice a problem until at some point (probably long after the program that stomped the address is no longer running and you're doing something else) when a divide-by-zero triggers and the interrupt jumps off into deep space.