=== death code ===
A routine whose job is to set everything in the computer --
registers, memory, flags, everything -- to zero, including that
portion of memory where it is running; its last act is to stomp on
its own " store zero " instruction. Death code isn't very useful,
but writing it is an interesting hacking challenge on architectures
where the instruction set makes it possible, such as the PDP-8 (it
has also been done on the DG Nova). Perhaps the ultimate death code
is on the TI 990 series, where all registers are actually in RAM,
and the instruction " store immediate 0 " has the opcode " 0 ". The
PC will immediately wrap around core as many times as it can until
a user hits HALT. Any empty memory location is death code. Worse,
the manufacturer recommended use of this instruction in startup
code (which would be in ROM and therefore survive).