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In computer science, an instruction set architecture (ISA) is an abstract model that generally defines how software controls the CPU in a computer or a family of computers. [1] A device or program that executes instructions described by that ISA, such as a central processing unit (CPU), is called an implementation of that ISA.
For conventional binary computers, machine code is the binary representation of a computer program which is actually read and interpreted by the computer. A program in machine code consists of a sequence of machine instructions (possibly interspersed with data). [1] Each machine code instruction causes the CPU to perform a specific task.
The instructions are usually part of an executable program, often stored as a computer file and executed on the processor. The x86 instruction set has been extended several times, introducing wider registers and datatypes as well as new functionality.
Upon power-on (a.k.a. booting), the processor initializes in real mode, and then begins executing instructions. Operating system boot code, which might be stored in read-only memory, may place the processor into the protected mode to enable paging and other features. Conversely, segment arithmetic, a common practice in real mode code, is not ...
A modern consumer CPU made by Intel: An Intel Core i9-14900KF Inside a central processing unit: The integrated circuit of Intel's Xeon 3060, first manufactured in 2006. A central processing unit (CPU), also called a central processor, main processor, or just processor, is the most important processor in a given computer.
An instruction set architecture (ISA) is an abstract model of a computer, also referred to as computer architecture.A realization of an ISA is called an implementation.An ISA permits multiple implementations that may vary in performance, physical size, and monetary cost (among other things); because the ISA serves as the interface between software and hardware.
The types of operations may include arithmetic, data copying, logical operations, and program control, as well as special instructions (e.g., CPUID). [10] In addition to the opcode, many instructions also specify the data (known as operands) the operation will act upon, although some instructions may have implicit operands or none at all. [10]
In computing, the instruction register (IR) or current instruction register (CIR) is the part of a CPU's control unit that holds the instruction currently being executed or decoded. [1] In simple processors, each instruction to be executed is loaded into the instruction register, which holds it while it is decoded, prepared and ultimately ...