Abstract To utilize the full potential of microprocessors, particularly the small and inexpensive single board systems, for dedicated data acquisition and instrumental system-control functions, it is imperative that researchers have an appreciation of the concepts for addressing, accessing and interfacing peripheral devices to microprocessor systems. These concepts are presented for the Intel 8080, 8085 and Mostek 6502 microprocessors with specific examples for the SDK 80 (8080), SDK 85 (8085) and KIM-1 (6502) single-board microprocessor systems. Features of the control bus architecture are discussed with regard to the movement of data to or from peripheral devices and memory. Utilization of control bus signals and addresses generated from the user program to address and access memory and peripheral devices are discussed and illustrated. The ability of these three microprocessors to handle and service interrupt requests from peripheral devices is discussed. The concepts for interfacing input and output peripheral devices, such as analogue-to-digital and digital-to-analogue converters, to these microprocessors are discussed and illustrated. Software programs suitable for use as subroutines, for input and output of data with these devices are presented and discussed.