This chapter provides an overview of single-board computers (SBCs) and microcontrollers (MCUs) focusing on their application for environmental monitoring. In particular, as an example, we look into building a data acquisition system (DAS) or a datalogger with an SBC and with an MCU, for example, using an MCU to monitor solar radiation (Mukaro and Carelse 1999). We start this chapter by reviewing terminology and basic concepts of computer organization and architecture (Null and Lobur 2012).