death code

death code

A routine whose job is to set everything in the computer -registers, memory, flags - to zero, including that portionof memory where it is running; its last act is to stomp on itsown "store zero" instruction. Death code isn't very useful,but writing it is an interesting hacking challenge onarchitectures 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 registers are actually in RAM, and theinstruction "store immediate 0" has the opcode 0. Theprogram counter will immediately wrap around core as manytimes as it can until a user hits HALT. Any empty memorylocation is death code. Worse, the manufacturer recommendeduse of this instruction in startup code (which would be inROM and therefore survive).