The Z80 orthogonalized this further by making all 16-bit register pairs, including IX and IY, more general purpose, as well as allowing 16-bit copying directly to and from memory for all of these pairs. The 16-bit IX and IY registers in the Z80 are primarily intended as base address-registers, where a particular instruction supplies a constant offset that is added to the previous values, but they are also usable as 16-bit accumulators, among other things. The Z80 also introduced a new signed overflow flag and complemented the fairly simple 16-bit arithmetics of the 8080 with dedicated instructions for "signed" 16-bit arithmetics.