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x86 memory segmentation. The Intel x86 computer instruction set architecture has supported memory segmentation since the original Intel 8086 in 1978. It allows programs to address more than 64 KB (65,536 bytes) of memory, the limit in earlier 80xx processors. In 1982, the Intel 80286 added support for virtual memory and memory protection; the ...
Memory segmentation is an operating system memory management technique of dividing a computer 's primary memory into segments or sections. In a computer system using segmentation, a reference to a memory location includes a value that identifies a segment and an offset (memory location) within that segment. Segments or sections are also used in ...
DS (data segment), CS (code segment), SS (stack segment), and ES (extra segment). Another 16-bit register can act as an offset into a given segment, and so a logical address on this platform is written segment:offset, typically in hexadecimal notation. In real mode, in order to calculate the physical address of a byte of memory, the hardware ...
Segment descriptor. In memory addressing for Intel x86 computer architectures, segment descriptors are a part of the segmentation unit, used for translating a logical address to a linear address. Segment descriptors describe the memory segment referred to in the logical address. [1] The segment descriptor (8 bytes long in 80286 and later ...
The stack segment register (SS) is usually used to store information about the memory segment that stores the call stack of currently executed program. SP points to current stack top. By default, the stack grows downward in memory, so newer values are placed at lower memory addresses. To save a value to the stack, the PUSH instruction is used.
Code segment. This shows the typical layout of a simple computer's program memory with the text, various data, and stack and heap sections. In computing, a code segment, also known as a text segment or simply as text, is a portion of an object file or the corresponding section of the program's virtual address space that contains executable ...
An odd offset would cause a program check (unless the base register itself also contained an odd address)—since instructions had to be aligned on half-word boundaries to execute without a program or hardware interrupt. The previous example describes an indirect way to address to a memory location in the format of segment:offset.
Memory address. 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 used at various levels by software and hardware. [1] Memory addresses are fixed-length sequences of digits conventionally displayed and ...