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The segment address is always added to a 16-bit offset in the instruction to yield a linear address, which is the same as physical address in this mode. For instance, the segmented address 06EFh:1234h (here the suffix "h" means hexadecimal ) has a segment selector of 06EFh, representing a segment address of 06EF0h, to which the offset is added ...
In a system using segmentation, computer memory addresses consist of a segment id and an offset within the segment. [3] A hardware memory management unit (MMU) is responsible for translating the segment and offset into a physical address, and for performing checks to make sure the translation can be done and that the reference to that segment and offset is permitted.
In computer engineering and low-level programming (such as assembly language), an offset usually denotes the number of address locations added to a base address in order to get to a specific absolute address. In this (original) meaning of offset, only the basic address unit, usually the 8-bit byte, is used to specify the offset's size.
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 ...
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 ...
The segment register acts as an index into a table, which provides an offset to be added to the virtual address. Except when using FS or GS, the OS ensures that the offset will be zero. After the offset is added, the address is masked to be no larger than 32 bits.
e. Real mode, also called real address mode, is an operating mode of all x86 -compatible CPUs. The mode gets its name from the fact that addresses in real mode always correspond to real locations in memory. Real mode is characterized by a 20- bit segmented memory address space (giving 1 MB of addressable memory) and unlimited direct software ...
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 fields: [2] A segment base address. The segment limit which specifies the segment size. Access rights byte containing the protection mechanism information.