Computer-On-Module, COMs are complete embedded computers built on a single circuit board. A COM is positioned between a full equipped computer and a microcontroller. The design is centered on a microprocessor with RAM, input/output controllers and all other features needed to be a functional computer on the one board. However, unlike a single-board computer, the COM usually lacks the standard connectors for any input/output peripherals to be attached directly to the board.

A COM usually needs to be mounted on a carrier board (or "baseboard") which breaks the bus out to standard peripheral connectors.

Portwell’s Computer-on-module series includes: COM Express, SMARC, Qseven, and ETX.