Instruction (computer science)
computer science, an instruction is a single operation of a processor defined by an instruction set architecture. In a broader sense, an "instruction" may be any representation of an element of an executable program, such as a bytecode.
On traditional architectures, an instruction includes an
opcodespecifying the operation to be performed, such as "add contents of memory to register", and zero or more operandspecifiers, which may specify registers, memory locations, or literal data. The operand specifiers may have addressing modes determining their meaning or may be in fixed fields.
very long instruction word(VLIW) architectures, which include many microcodearchitectures, multiple simultaneous operations and operands are specified in a single instruction.
The size or length of an instruction varies widely, from as little as four bits in some
microcontrollers to many hundreds of bits in some VLIW systems. Most modern processors used in personal computers, mainframes, and supercomputers have instruction sizes between 16 and 64 bits. In some architectures, notably most Reduced Instruction Set Computers, instructions are a fixed length, typically corresponding with that architecture's word size. In other architectures, instructions have variable length, typically integral multiples of a byteor a halfword.
The instructions constituting a program are rarely specified using their internal, numeric form; they may be specified by programmers using an
assembly languageor, more commonly, may be generated by compilers.
Wikimedia Foundation. 2010.
Look at other dictionaries:
computer science — computer scientist. the science that deals with the theory and methods of processing information in digital computers, the design of computer hardware and software, and the applications of computers. [1970 75] * * * Study of computers, their… … Universalium
Computer science — or computing science (abbreviated CS) is the study of the theoretical foundations of information and computation and of practical techniques for their implementation and application in computer systems. Computer scientists invent algorithmic… … Wikipedia
computer science — noun the branch of engineering science that studies (with the aid of computers) computable processes and structures • Syn: ↑computing • Topics: ↑computer, ↑computing machine, ↑computing device, ↑data processor, ↑electronic computer, ↑ … Useful english dictionary
COMPUTER SCIENCE — The term Computer Science encompasses three different types of research areas: computability, efficiency, and methodology. General Introduction Computability deals with the question of what is mechanically computable. The most natural way to… … Encyclopedia of Judaism
Thrash (computer science) — In computer science, thrash (verb), is the term used to describe a degenerate situation on a computer where increasing resources are used to do a decreasing amount of work. In this situation the system is said to be thrashing . Usually it refers… … Wikipedia
Thrashing (computer science) — In computer science, thrashing is a situation where large amounts of computer resources are used to do a minimal amount of work, with the system in a continual state of resource contention. Once started, thrashing is typically self… … Wikipedia
Thread (computer science) — This article is about the concurrency concept. For the multithreading in hardware, see Multithreading (computer architecture). For the form of code consisting entirely of subroutine calls, see Threaded code. For other uses, see Thread… … Wikipedia
Vectorization (computer science) — Vectorization, in computer science, is the process of converting a computer program from a scalar implementation, which does an operation on a pair of operands at a time, to a vectorized program where a single instruction can perform multiple… … Wikipedia
Kernel (computer science) — In computer science, the kernel is the central component of most computer operating systems (OS). Its responsibilities include managing the system s resources (the communication between hardware and software components). As a basic component of… … Wikipedia
Optimization (computer science) — In computing, optimization is the process of modifying a system to make some aspect of it work more efficiently or use fewer resources. For instance, a computer program may be optimized so that it executes more rapidly, or is capable of operating … Wikipedia