On this page I have placed links to documentation, source code, and Demo DSK images in order for an interested user to discover the fun that I have had in creating DOS 4.1, DOS 4.3, and DOS 4.5.  I will add more documentation and software links as I prepare the files.  Just click on the link and the file will download to your computer’s desktop.  The Demo and Tools Diskettes are bootable.  A TAR file should extract its content when you double-click on its image after the download completes.  Please contact me if you have any difficulty extracting a TAR file.  Software applications and utilities that are specific to DOS 4.3 are contained in the DOS 4.3 Source Code TAR file and software applications and utilities that are specific to DOS 4.5 are contained in the DOS 4.5 Source Code TAR file.  I have recently developed Client/Server software that will transfer a volume image up to 48 tracks, where each track may have 16 or 32 sectors, from one Apple computer or emulated computer to another Apple computer or emulated computer.  DOS 4.3 or DOS 4.5 may be utilized since volume phase is now available in both of these versions of DOS.  The DOS 4.1 Disk Operating System Second Edition, the DOS 4.3 File Management System, the DOS 4.5 File and Volume Disk Management System, and the DOS 4.5 Volume and File Disk Management System Second Edition books may be purchased directly from the Lulu.com bookstore.  Using Complex Numbers in an Apple ][ Computer is now available for download.  The Complex Math.tar file contains a PDF and all source code and example programs.