64-bit computing 64-bit computing In computer architecture, 64-bit computing is the use of processors that have datapath widths, integer size, and memory address widths of 64 bits (eight octets). Also, 64-bit computer architectures for central processing units (CPUs) and arithmetic logic units (ALUs) are those that are based on processor registers, address buses, or data buses of that size. From the software perspective, 64-bit computing means the use of code with 64-bit virtual memory addresses. However, not all 64-bit instruction sets support full 64-bit virtual memory addresses; x86-64 and ARMv8, for example, support only 48 bits of virtual address, with the remaining
Byte addressing systems, such as the PDP-10, use word addressing but facilitate access to individual bytes using special instructions which can access memory using a "byte pointer", which contains both a word address and the index of a specific byte within the word. Byte addressing Byte addressing refers to hardware architectures which support accessing individual bytes of data rather than only larger units called words, which would be "word-addressable". Such computers are sometimes called "byte machines" (in contrast to "word machines"). The basic unit of digital storage is called a bit, storing a single 0 or 1. Many common architectures can address