The time period during which one instruction is fetched from memory and executed when a computer is given an instruction in machine language. There are typically four stages of an instruction cycle that the CPUcarries out:
Fetch the instruction from memory. This step brings the instruction into the instruction register, a circuit that holds the instruction so that it can be decoded and executed.
Decode the instruction.
Read the effective address from memory if the instruction has an indirect address.
Execute the instruction.
Steps 1 and 2 are called the fetch cycle and are the same for each instruction. Steps 3 and 4 are called the execute cycleand will change with each instruction.
The term refers to both the series of four steps and also the amount of time that it takes to carry out the four steps.
An instruction cycle also is called machine cycle.
- instruction register
See under instruction cycle.
- instruction set
(n.) Also called a command set, the basic set of commands, or instructions, that a microprocessor understands. One of the principal characteristics that separates RISC from CISC microprocessors is the size of the instruction set — RISC microprocessors have relatively small instruction sets whereas CISC processors have relatively large instruction sets.
A whole number. The following are integers: 0 1 -125 144457 In contrast, the following are not integers: 5.34 -1.0 1.3E4 “string” The first three are floating-point numbers; the last is a character string. Integers, floating-point numbers, and character strings constitute the basic data types that most computers support. There are often different sizes of […]
- integrated HDTV
A high-definition television or display that has the HDTV tuner built into the set. It does not need a separate set-top box to receive over-the-air HDTV signals.
(1) A popular computer buzzword that refers to two or more components merged together into a single system. For example, any software product that performs more than one task can be described as integrated. (2) Increasingly, the term integrated software is reserved for applications that combine word processing, database management, spreadsheet functions, and communications into […]