What does microcode mean?
Microcode is a compact set of low-level instructions that helps a computer processor carry out a more complex machine instruction. Rather than performing a requested operation immediately, a processor may consult stored microcode that specifies the sequence of simpler internal steps required. This arrangement can make complex instruction sets easier to design, implement, and maintain, although it may also affect processor speed and hardware complexity. The word can also be used more generally for a very small body of program code, though its technical meaning dominates in discussions of central processing units, control stores, and computer architecture. Microcode is related to, but distinct from, machine code: machine instructions are the operations exposed to software, while microcode controls how the hardware realizes those operations. It is likewise not synonymous with firmware, which is persistent software stored in a device rather than a particular processor-control mechanism.
nounA very small set of instructions used to implement a larger set of machine operations. In computing, microcode is typically stored in a processor or control memory and is read by the hardware when it needs to carry out a particular operation.
- A low-level sequence of instructions used by a processor to control the internal operations needed to execute a higher-level machine instruction.
- Any very small body of program code or instructions.
"The processor uses microcode to control the internal steps required to execute a complex instruction."
"Engineers updated the processor's microcode to correct an instruction error."
"The new design replaces the lengthy sequence of manual steps with compact microcode."
Plural forms are used for separate microcode sets or distinct collections of microcode; this is uncommon in ordinary technical prose.
"The manufacturer released corrected microcodes for several processor models."
Microcode acts like a tiny rulebook inside a processor, translating each visible instruction into a sequence of simpler internal steps.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does microcode come from?
The word combines the combining form micro-, meaning small or extremely small, with code, a term for a system of instructions used by a computer. The form reflects the traditional use of the prefix for very small scales and units. Microcode arose as a specialized computing term for small instruction sequences used to implement more complex processor operations, and it became especially associated with the control stores of early and later computer architectures.
Related word forms
How microcode is actually used
The term is most common in computing and electronics. It usually refers to control instructions for a processor, and it should not be used as a general synonym for a small program unless the context makes that meaning clear.
Easily confused with microcode
Machine code consists of instructions executed directly by a processor, whereas microcode is lower-level control code that helps the processor implement those instructions.
Firmware is persistent software stored in a device, while microcode is a specific low-level mechanism used to control processor operations.