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In a segmented architecture computer, a far pointer is a pointer to memory in a specific context, [1] such as a segment selector making it possible to point to addresses outside of the default segment.
Comparison and arithmetic on far pointers is problematic: there can be several different segment-offset address pairs pointing to one physical address.
For example, in an Intel 8086, as well as in later processors running 16-bit code, a far pointer has two parts: a 16-bit segment value, and a 16-bit offset value. A linear address is obtained by shifting the binary segment value four times to the left, and then adding the offset value. Hence the effective address is 21 bits [Note 1] . There can be up to 4096 different segment-offset address pairs pointing to one physical address. To compare two far pointers, they must first be converted (normalized) to their linear representation.
On C compilers targeting the 8086 processor family, far pointers were declared using a non-standard far qualifier; e.g., charfar*p; defined a far pointer to a char. The difficulty of normalizing far pointers could be avoided with the non-standard huge qualifier. On other compilers it was done using an equally non-standard __far qualifier. [2]
Example of far pointer:
#include<stdio.h>intmain(){charfar*p=(charfar*)0x55550005;charfar*q=(charfar*)0x53332225;*p=80;(*p)++;printf("%d",*q);return0;}p is : 0x5555 * 0x10 + 0x0005 = 0x55555q is : 0x5333 * 0x10 + 0x2225 = 0x55555p and q both point to the same location 0x55555.IA-32 is the 32-bit version of the x86 instruction set architecture, designed by Intel and first implemented in the 80386 microprocessor in 1985. IA-32 is the first incarnation of x86 that supports 32-bit computing; as a result, the "IA-32" term may be used as a metonym to refer to all x86 versions that support 32-bit computing.
The 8086 is a 16-bit microprocessor chip designed by Intel between early 1976 and June 8, 1978, when it was released. The Intel 8088, released July 1, 1979, is a slightly modified chip with an external 8-bit data bus, and is notable as the processor used in the original IBM PC design.
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