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In 8-bit CP/M versions it is located in the first 256 bytes of memory, hence its name. The equivalent structure in DOS is the Program Segment Prefix (PSP), a 256-byte (page-sized) structure, which is by default located exactly before offset 0 of the program's load segment, rather than in segment 0.
In computer architecture, 256-bit integers, memory addresses, or other data units are those that are 256 bits (32 octets) wide. Also, 256-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers , address buses , or data buses of that size.
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 bytes of memory specially, [1] whereas many other processors do not.
In a computer using virtual memory, accessing the location corresponding to a memory address may involve many levels. In computing, a memory address is a reference to a specific memory location in memory used by both software and hardware. [1] These addresses are fixed-length sequences of digits, typically displayed and handled as unsigned ...
The address and value parameters may contain expressions, as long as the evaluated expressions correspond to valid memory addresses or values, respectively.A valid address in this context is an address within the computer's address space, while a valid value is (typically) an unsigned value between zero and the maximum unsigned number that the minimum addressable unit (memory cell) may hold.
Note that this is more or less the same as base-plus-offset addressing mode, except that the offset in this case is large enough to address any memory location. Example 1: Within a subroutine, a programmer may define a string as a local constant or a static variable. The address of the string is stored in the literal address in the instruction.
In DOS 1.x, it was necessary for the CS (Code Segment) register to contain the same segment as the PSP at program termination, thus standard programming practice involved saving the DS register (since the DS register is loaded with the PSP segment) along with a zero word to the stack at program start and terminating the program with a RETF instruction, which would pop the saved segment value ...
1,024 bits (128 bytes) - RAM capacity of the Atari 2600: 1,288 bits (161 bytes) – approximate maximum capacity of a standard magnetic stripe card: 2 11: 2,048 bits (256 bytes) – RAM capacity of the stock Altair 8800: 2 12: 4,096 bits (512 bytes) – typical sector size, and minimum space allocation unit on computer storage volumes, with ...