Difference between revisions of "Instruction"
From Computer History Wiki
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An '''instruction''' is, at the highest level of abstraction, the smallest unit of computation which a [[programmer]] can direct the [[Central Processing Unit|CPU]] to perform. | An '''instruction''' is, at the highest level of abstraction, the smallest unit of computation which a [[programmer]] can direct the [[Central Processing Unit|CPU]] to perform. | ||
| − | In more practical terms, the CPU operates by fetching items from [[main memory]]; each item contains a single directive for the CPU (e.g. | + | In more practical terms, the CPU operates by fetching items from [[main memory]]; each item contains a single directive for the CPU (e.g. add the contents of one [[register]] to another, or move a unit of data from a register, to main memory) - those items are instructions. (An instruction is usually a [[word]], but on some CPUs, multiple instructions could be packed in each word, while on others, some instructions took multiple words.) |
| − | Some computers | + | Some early computers used the alternative term '''order''' for instructions. |
{{semi-stub}} | {{semi-stub}} | ||
[[Category: CPU Basics]] | [[Category: CPU Basics]] | ||
Revision as of 13:04, 3 June 2023
An instruction is, at the highest level of abstraction, the smallest unit of computation which a programmer can direct the CPU to perform.
In more practical terms, the CPU operates by fetching items from main memory; each item contains a single directive for the CPU (e.g. add the contents of one register to another, or move a unit of data from a register, to main memory) - those items are instructions. (An instruction is usually a word, but on some CPUs, multiple instructions could be packed in each word, while on others, some instructions took multiple words.)
Some early computers used the alternative term order for instructions.
