The purpose of this paper is to introduce the reader to the concepts and techniques required to write a device driver for a character class device on the Micro Channel Architecture (MCA) bus in Version 3.xx of IBM's AIX operating system (denoted by just AIX in this document). It attempts to tie together the major pieces of development information dispersed throughout the AIX manuals. It also includes some information not found in the manuals which is crucial to the development of a working device driver. This document by no means provides complete coverage of the topic, and references for further information will be made liberally throughout. It may best be regarded as a road map to AIX device driver development. The reader is assumed to be proficient in UNIX/AIX applications programming and the C programming language.