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The x86 processors support five modes of operation for x86 code, Real Mode, Protected Mode, Long Mode, Virtual 86 Mode, and System Management Mode, in which some instructions are available and others are not. A 16-bit subset of instructions is available on the 16-bit x86 processors, which are the 8086, 8088, 80186, 80188, and 80286.
existing instructions extended to a 64 bit address size (JRCXZ) existing instructions extended to a 64 bit operand size (remaining instructions) Most instructions with a 64 bit operand size encode this using a REX.W prefix; in the absence of the REX.W prefix, the corresponding instruction with 32 bit operand size is encoded. This mechanism also ...
FASM (flat assembler) is an assembler for x86 processors. It supports Intel-style assembly language on the IA-32 and x86-64 computer architectures. It claims high speed, size optimizations, operating system (OS) portability, and macro abilities. [2] [3] It is a low-level assembler [3] and intentionally uses very few command-line options.
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The FLAGS register is the status register that contains the current state of an x86 CPU.The size and meanings of the flag bits are architecture dependent. It usually reflects the result of arithmetic operations as well as information about restrictions placed on the CPU operation at the current time.
The Netwide Assembler (NASM) is an assembler and disassembler for the Intel x86 architecture. It can be used to write 16-bit, 32-bit and 64-bit programs. It is considered one of the most popular assemblers for Linux and x86 chips. [3] It was originally written by Simon Tatham with assistance from Julian Hall.
AMD's 64-bit extension to the original instruction set make relatively few changes to 32-bit addressing, with the most significant being that in long mode, 64-bit addressing is the default. 64-bit registers (RAX, RBX, RCX, etc.) are used rather than 32-bit registers for address computation. The displacement is not widened to 64 bits; MOD=11 ...
Microsoft Macro Assembler (MASM) is an x86 assembler that uses the Intel syntax for MS-DOS and Microsoft Windows.Beginning with MASM 8.0, there are two versions of the assembler: One for 16-bit & 32-bit assembly sources, and another (ML64) for 64-bit sources only.