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x86 assembly language includes instructions for a stack-based floating-point unit (FPU). The FPU was an optional separate coprocessor for the 8086 through the 80386, it was an on-chip option for the 80486 series, and it is a standard feature in every Intel x86 CPU since the 80486, starting with the Pentium.
Below is the full 8086/8088 instruction set of Intel (81 instructions total). [2] These instructions are also available in 32-bit mode, in which they operate on 32-bit registers (eax, ebx, etc.) and values instead of their 16-bit (ax, bx, etc.) counterparts.
Whereas the 8086 was a 16-bit microprocessor, it used the same microarchitecture as Intel's 8-bit microprocessors (8008, 8080, and 8085). This allowed assembly language programs written in 8-bit to seamlessly migrate. [7] New instructions and features — such as signed integers, base+offset addressing, and self-repeating operations — were added.
x86 (also known as 80x86 [3] or the 8086 family [4]) is a family of complex instruction set computer (CISC) instruction set architectures [a] initially developed by Intel, based on the 8086 microprocessor and its 8-bit-external-bus variant, the 8088.
In computer programming, assembly language (alternatively assembler language [1] or symbolic machine code), [2] [3] [4] often referred to simply as assembly and commonly abbreviated as ASM or asm, is any low-level programming language with a very strong correspondence between the instructions in the language and the architecture's machine code instructions. [5]
Furthermore, on a modern x86 system, BIOS calls can only be performed in Real mode, or Virtual 8086 mode. v8086 is not an option in Long mode. This means that a modern operating system, which operates in Protected mode (32 bit), or Long mode (64 bit), would need to switch into real mode and back to call the BIOS - a hugely expensive operation.
In the x86 assembly language, the TEST instruction performs a bitwise AND on two operands. The flags SF, ZF, PF are modified while the result of the AND is discarded. The OF and CF flags are set to 0, while AF flag is undefined. There are 9 different opcodes for the TEST instruction depending on the type and size of the operands. It can compare ...
Michael Abrash was a columnist in the 1980s for the magazine Programmer's Journal.The articles were collected in the 1989 book, Power Graphics Programming.His second book, Zen of Assembly Language Volume 1: Knowledge (1990), [13] is about writing efficient assembly code for the 16-bit 8086 processor, but was released after the 80486 CPU was already being used in IBM PC compatibles. [14]