Editing Zero page (section)

{{Short description|Memory page starting at address zero}}

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The '''zero page''' or '''base page''' is the block of memory at the very beginning of a [[computer]]'s [[address space]]; that is, the [[page (computer memory)|page]] whose starting address is zero. The size of a page depends on the context, and the significance of zero page memory versus higher addressed memory is highly dependent on machine architecture. For example, the [[Motorola 6800]] and [[MOS Technology 6502]] processor families treat the first 256 [[byte]]s of [[Computer memory|memory]] specially,<ref name="Student Papers in Computer Architecture"/> whereas many other processors do not.

Unlike more modern hardware, in the 1970s computer [[random-access memory|RAM]] speed was similar to that of  CPUs.{{fact|date=September 2022}} Thus it made sense to have few registers and use the main memory as an extended pool of extra registers. In machines with a relatively wide [[16-bit]] [[address bus]] and comparatively narrow [[8-bit]] [[bus (computing)|data bus]], calculating an address in memory could take several cycles. The zero page's one-byte address was smaller and therefore faster to read and calculate than other locations, making the zero page useful for high-performance code.

Zero page addressing now has mostly historical significance, since the developments in [[integrated circuit]] [[technology]] have made adding more registers to a CPU less expensive and CPU operations much faster than RAM accesses.