Search results
Results from the WOW.Com Content Network
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.
However, segment registers are usually used implicitly. All CPU instructions are implicitly fetched from the code segment specified by the segment selector held in the CS register. Most memory references come from the data segment specified by the segment selector held in the DS register. These may also come from the extra segment specified by ...
Four registers are used to refer to four segments on the 16-bit x86 segmented memory architecture. 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 ...
A reference to a memory location includes a value that identifies a segment and an offset within that segment. A segment descriptor may limit access rights, e.g., read only, only from certain rings. The x86 architecture has multiple segmentation features, which are helpful for using protected memory on this architecture. [1]
It is technically possible to use up to 256 KB of memory for code and data, with up to 64 KB for code, by setting all four segment registers once and then only using 16-bit offsets (optionally with default-segment override prefixes) to address memory, but this puts substantial restrictions on the way data can be addressed and memory operands ...
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) contains the following ...
The Intel 8086 family of CPUs provided four segments: the code segment, the data segment, the stack segment and the extra segment. Each segment was placed at a specific location in memory by the software being executed and all instructions that operated on the data within those segments were performed relative to the start of that segment.
Segment registers, fundamental to the older 8088 and 80286 MMU designs, are not used in modern OSes, with one major exception: access to thread-specific data for applications or CPU-specific data for OS kernels, which is done with explicit use of the FS and GS segment registers. All memory access involves a segment register, chosen according to ...