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Pointer formats are known as near, far, or huge. Near pointers are 16-bit offsets within the reference segment, i.e. DS for data and CS for code. They are the fastest pointers, but are limited to point to 64 KB of memory (to the associated segment of the data type). Near pointers can be held in registers (typically SI and DI).
Here is a simple example of index register use in assembly language pseudo-code that sums a 100 entry array of 4-byte words: Clear_accumulator Load_index 400,index2 //load 4*array size into index register 2 (index2) loop_start : Add_word_to_accumulator array_start,index2 //Add to AC the word at the address (array_start + index2) Branch_and_decrement_if_index_not_zero loop_start,4,index2 //loop ...
x86-64 (also known as x64, x86_64, AMD64, and Intel 64) [note 1] is a 64-bit extension of the x86 instruction set architecture first announced in 1999. It introduces two new operating modes: 64-bit mode and compatibility mode, along with a new four-level paging mechanism.
Microsoft and Sun Microsystems/Oracle also use term "x64", while many Linux distributions, and the BSDs also use the "amd64" term. Microsoft Windows, for example, designates its 32-bit versions as "x86" and 64-bit versions as "x64", while installation files of 64-bit Windows versions are required to be placed into a directory called "AMD64". [20]
x86 assembly language is a family of low-level ... Image base = 0x00400000 %define ... the given target address into the instruction pointer to, so, for example, ...
A computer program can access an address given explicitly – in low-level programming this is usually called an absolute address, or sometimes a specific address, and is known as pointer data type in higher-level languages. But a program can also use relative address which specifies a location in relation to somewhere else (the base address).
Increment shadow stack pointer 3 Tiger Lake, Zen 3: INCSSPQ r64: F3 REX.W 0F AE /5: RDSSPD r32: F3 0F 1E /1: Read shadow stack pointer into register (low 32 bits) [a] RDSSPQ r64: F3 REX.W 0F 1E /1: Read shadow stack pointer into register (full 64 bits) [a] SAVEPREVSSP: F3 0F 01 EA: Save previous shadow stack pointer RSTORSSP m64: F3 0F 01 /5
The x86-64 architecture does not use segmentation in long mode (64-bit mode). Four of the segment registers, CS, SS, DS, and ES, are forced to base address 0, and the limit to 2 64. The segment registers FS and GS can still have a nonzero base address. This allows operating systems to use these segments for special purposes.