DOS 4.1 is a newly imagined Disk Operating System for the Apple ][ computer, initially released in 2018. When the DOS 4.1 Manual was published, DOS 4.1 was not yet finished until Build 46 was completed in 2019. Designed and programmed by Walland Philip Vrbancic, Jr., a professional programmer and Electrical Engineer since 1983, DOS 4.1 contains the power and the flexibility he always thought DOS should have while remaining essentially compatible with DOS 3.3. DOS 4.1 Disk Operating System Second Edition describes all of the features that comprise DOS 4.1L and DOS 4.1H, including those features introduced by Build 46, using redesigned Tables, Figures, Schematic Diagrams, and example Assembly Language Routines. The following list are some of the features that have been engineered into the second edition of the DOS 4.1 Disk Operating System. DOS 4.1H boots directly into Language Card memory and sets HIMEM to 0xBE00. All five of its file buffers are fully contained in Language Card memory. DOS 4.1 supports the full 65C02 instruction set and it can now be used in both the Lisa and the Big Mac assemblers. Sourceror and Big Mac both support all SWEET16 opcodes. The ROM image described in this book supports the 65C02, SWEET16, and GARBAGE based on BongersÕ algorithm. DOS 4.1 supports most Clock Cards which play an integral role in Volume and File timestamps. Volumes may be titled, numbered, and initialized to boot or to store files and data exclusively. Even track 0x00 is used to store files and data. Files are loaded into memory and saved using a page-accelerated algorithm. DOS 4.1 supports Applesoft CHAIN, File DIFF, File GREP, File LIST, File Undelete, Sector Display, Syntactical HELP (only in DOS 4.1H), and full lowercase command and argument input. DOS 4.1 has an expanded File Manager with additional Opcodes, and the Boot and Volume INIT functions utilize the same BOOTCFG Table. The Volume Catalog may use a minimum of a single sector and the CATALOG output may be terminated by pressing the ESC key at any time. DOS 4.1 uses the B keyword to implement the ÒFile Delete/File SaveÓ strategy for disk space conservation. DOS 4.1 can read DOS 3.3 Volumes, files, and data. DOS 4.1 can easily initialize Volumes with up to 48 tracks having either 16 or 32 sectors per track. All the source code and all the schematics can be requested through www.applecored.net.
