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Encyclopedia > Instruction (computer science)

In computer science, an instruction typically refers to a single operation of a processor within a computer architecture. The types of instruction allowed are defined and determined within the particular platform's instruction set architecture (ISA), which also determines register sources and destination operands, and perhaps an immediate field. Machine instructions are numbers represented in binary. A portion (field) of the instruction designates the operation to be done and is called an opcode; since the numeric value of this is not very meaningful to humans, a corresponding short abbreviation is used by programmers. The size, or "width" of an instruction depends on the architecture of the platform, but it is usually from 4 to 64 bits wide. The following is an example of a x86 instruction in symbolic assembler notation: Computer science is the study of information and computation. ... Intel 80486DX2 microprocessor in a ceramic PGA package A central processing unit (CPU), or sometimes simply processor, is the component in a digital computer that interprets instructions and processes data contained in software. ... In computer science, computer architecture is the conceptual design and fundamental operational structure of a computer system. ... An instruction set, or instruction set architecture (ISA), describes the aspects of a computer architecture visible to a programmer, including the native datatypes, instructions, registers, addressing modes, memory architecture, interrupt and exception handling, and external I/O (if any). ... In computer architecture, a processor register is a small amount of very fast computer memory used to speed the execution of computer programs by providing quick access to commonly used values—typically, the values being in the midst of a calculation at a given point in time. ... The binary numeral system (base-2) represents numeric values using two symbols, typically 0 and 1. ... Microprocessors perform operations using binary bits (on/off/1or0). ... A programmer or software developer is someone who programs computers, i. ... In computing, a platform describes some sort of framework, either in hardware or software, which allows software to run. ... This article is about the unit of information. ... x86 or 80x86 is the generic name of a microprocessor architecture first developed and manufactured by Intel. ... An assembler is a computer program for translating assembly language — essentially, a mnemonic representation of machine language — into object code. ...

SHL   AX, 01

SHL is called the operation, and AX, 01 are called operands. AX is the name of a register, 01 is a constant. In this example, SHL is a mnemonic abbreviation for "shift left". The instruction causes the value in AX to be shifted left by 01 bit postition. Programming languages generally have a set of operators that perform arithmetical operations, and others such as boolean operations on truth values, and string operators manipulating strings of text. ... In mathematics, an operand is one of the inputs of an operator. ... In computer science and mathematics, a variable is a symbol denoting a quantity or symbolic representation. ... A mnemonic (pronounced in American English, in British English) is a memory aid. ...


See also: Machine language A system of codes directly understandable by a computers CPU is termed this CPUs native or machine language. ...


  Results from FactBites:
 
Computer - definition of Computer in Encyclopedia (3757 words)
Computers are based on the application of known physical properties and their interactions to represent some aspect or aspects of the problem at hand, so that the mechanical interactions will automatically produce a solution to the problem.
Computers may directly model the problem being solved, in the sense that the problem being solved is mapped as closely as possible onto the physical phenomena being exploited.
Computers with general-purpose capabilities are called Turing-complete and this status is often used as the threshold capability that defines modern computers, however, this definition is problematic.
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