The PDP-11's 16-bit addresses can address 64 KB. By the time the PDP-11 yielded to the VAX, 8-bit bytes and hexadecimal notation were becoming standard in the industry; however, numeric values on the PDP-11 always use octal notation, and the amount of memory attached to a PDP-11 is always stated as a number of words. The basic logical address space is 32K words, but the high 4K (addresses 1600008 through 1777778) are not populated because input/output registers on the bus responded to addresses in that range. So originally, a fully loaded PDP-11 had 28K words.