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x86 assembly language is a family of low-level programming languages that are used to produce object code for the x86 class of processors. These languages provide backward compatibility with CPUs dating back to the Intel 8008 microprocessor, introduced in April 1972.
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 ...
The great leap toward 64-bit computing and the maintenance of backward compatibility with 32-bit and 16-bit software enabled the x86 architecture to become an extremely flexible platform today, with x86 chips being utilized from small low-power systems (for example, Intel Quark and Intel Atom) to fast gaming desktop computers (for example ...
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.
For example, the x86 architecture has available the 0x90 opcode; it is represented as NOP in the assembly source code. While it is possible to write programs directly in machine code, managing individual bits and calculating numerical addresses is tedious and error-prone. Therefore, programs are rarely written directly in machine code.
For example, the Intel Pentium and the AMD Athlon implement nearly identical versions of the x86 instruction set, but they have radically different internal designs. The concept of an architecture, distinct from the design of a specific machine, was developed by Fred Brooks at IBM during the design phase of System/360.
This article describes the calling conventions used when programming x86 architecture microprocessors. Calling conventions describe the interface of called code: The order in which atomic (scalar) parameters, or individual parts of a complex parameter, are allocated; How parameters are passed (pushed on the stack, placed in registers, or a mix ...