In order to provide the maximum level of hardware independence for the OS/2 Version 2.0 operating system, device driver are used to communicate with hardware devices. This concept is not new, and has been implemented in previous versions of OS/2 and in the DOS operating system. However, the implementation of device drivers under OS/2 Version 2.0 differ in several significant ways from that seen in previous versions. This chapter describes the implementation of device drivers under OS/2 Version 2.0.