Source : Free On-Line Dictionary of Computing

death code
     
        A routine whose job is to set everything in the computer -
        {register}s, memory, flags - 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} or the {Data General} {Nova}.
     
        Perhaps the ultimate death code is on the {TI 990} series,
        where all {register}s are actually in {RAM}, and the
        instruction "store immediate 0" has the {opcode} 0.  The
        {program counter} 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).
     
        [{Jargon File}]