Of the more than ten billion new processors manufactured last year, only about 2% became the brains of new PCs, Macs, and Unix workstations. The other 9.8 billion went into embedded systems. The essence of every modern electronic device, from toys to traffic lights to nuclear power plant controllers, these processors help run factories, manage weapon systems, and enable the worldwide flow of information, products, and people.

Embedded processors span the range from simple 4-bit microcontrollers like those at the heart of a greeting card or children's toy, to powerful custom 128-bit microprocessors and specialized DSPs and network processors. Some of the products that include these chips run a short assembly program from ROM with no operating system; many more run real-time operating systems and complex multithreaded C or C++ programs; and it's also increasingly common to find variants of desktop-lite operating systems based on Linux and Windows controlling more powerful devices that are still clearly embedded systems.

Virtually every electronic device designed and manufactured today is an embedded system, and virtually no first-world person is untouched by this technology. In fact, once you start looking for them, we're sure you can quickly find a few dozen embedded systems in your home and at least a few on your person. Yet, despite their ubiquity, remarkably few non-engineers have heard the word "embedded" used in this context. Fewer still could tell you which of the embedded systems they own or use are also real-time systems.


Though the use of embedded processors is now a practice more than three decades old, there's been no previous attempt to gather all its vocabulary in one place and clarify the meanings and usage of individual terms. This free online glossary provides the precise definitions needed to use embedded systems terminology properly.

Each definition begins with the part of speech and, where it's not obvious, standard pronunciation. The first sentence is a concise statement of that term's meaning. The concise definition is followed by any abbreviations, alternative terms or, in the case of an acronym for example, expansions. Depth and helpful diagrams, schematics, figures, equations, and code listings follow. When available, there are links to other online sources with additional information. Internally, everything is cross-referenced to the extent it's helpful.

The definitions are sorted alphabetically, so just click on a letter in the outline below to get started.


Though originally based on the glossary in the book Programming Embedded Systems in C and C++ and then a subset of the print Embedded Systems Dictionary, this online version has grown considerably and is a living reference. If you wish to cite it in your work, you may find the following MLA-style information helpful:

Barr, Michael. "Embedded Systems Glossary." Online at