This book is Volume 3 of the series FYSOS Operating System Design and will show the reader how to detect initialize and communicate with three of the most common media hardware devices the Floppy Disk Controller the IDE Hard Disk Controller and the SATA AHCI Hard Disk Controller. The reader will learn how to detect the controller what type of controller it is initialize it to default values detect attached devices and then communicate with those devices such as reading and writing to the attached media.All of this is done without any outside help such as operating system calls or the help of the BIOS. The reader will learn how to communicate with the hardware directly reading and writing to the system bus to achieve these tasks.The companion CDROM contains complete source code of each example within the book showing how to accomplish these tasks.This book and its companion series of books does not expect you to build the next great wonder of the computer world.