DOS 3.4 - Beta software

Welcome to DOS 3.4, a new OS for the Apple II in 2018.

A product, a proof of concept, or a project: DOS 3.4 is each of them. You may wonder why we have decided to upgrade/enhance DOS 3.3 (the January 1983 version), by providing that version, especially as we are more GS/OS users. This is beta software, please test, report bugs, and requested features!
You may also wonder what differs in DOS 3.4 from DOS 3.3. We compile the answers in that page.

Why DOS 3.4?
After the work on DOS 4.4, we realized that users were waiting for an update to DOS 3.3. There are plenty of other updates to DOS 3.3 out there, so why not make our own version?


What is DOS 3.4?

  • Disk structure:
    • A 5.25" floppy disk of 35 tracks of 16 sectors, for a total of 143Kb
    • The same commands as in DOS 3.3: INIT, CATALOG and the others with the same parameters
    • The new CAT command to display the catalog with no pause in the display
    • The support of lower-case commands and parameters. Filenames remain upper-case for compatibility.
  • Layer separation:
    • DOS patches previously buried in the RWTS are now in the OS code
    • The RWTS contains disk routines only!

What are the changes?

  • DOS 3.3 patches are now in the OS code ($1D00..$35FF)
  • Due to a lack of space, the error routine and messages have been replaced and display the error code only
  • The RWTS contains disk routines only!

What could be the next steps?

  • Please test and report bugs!
  • Master utility does not recognize the OS as a master, need to correct!
  • Make it faster and avoid using an intermediate buffer ($3E..$3F is the key)
  • Deliver the working source code of DOS 3.4
  • Make error messages more user friendly (err #0 is the beep, others are messages...)
  • Add new features...

What are the files provided?

  • DOS 3.4 Master disk
    This is the new DOS 3.4 master disk!


  • Book: Apple II DOS 3.3 Guide du programmeur, Marcel Cottini, SYBEX

Download :

DOS 3.4 Master disk