In a stack machine, the operands used in the instructions are always at a known offset (set in the stack pointer), from a fixed location (the bottom of the stack, which in a hardware design might always be at memory location zero), saving precious in-cache or in-CPU storage from being used to store quite so many memory addresses or index numbers. This leads to an instruction set architecture (ISA) style known as a zero address format, and may preserve such registers and cache for use in non-flow computation.