A short story on the V50 DOS Library
By Colin. J. Wenzel

From the very beginning, AmigaDOS has always been the orphaned child in the Amiga operating system.

In the early days, the addition of the TRIPOS kernel as the basis for the Amiga Disk Operating System (DOS) was not the first choice, but circumstances being what they were, we finished up with TRIPOS, written in a language called BCPL.

BCPL was a predecessor to modern C language and whether they realized it at the time or not, C was eventually to become the pseudo standard language for the entire Amiga Operating system and various components, as well as being a favored language for writing a vast number of applications.

Of course, at the time, nearly all of the OS components were written in MC68000 Assembly Language, this of course, was not a great problem in those days as most programmers in the early Amiga history were brought up using assembly code, myself being one of them, besides, there was no roadmap to move the OS to any other processor at the time and the need for speed was of primary consideration, portability was not.

But times change, and soon some parts of the Amiga operating system were added during subsequent releases and some parts were rewritten in C. However, the larger part of the OS was still in MC68000 assembly code, also, the legacy of BCPL TRIPOS stayed with us to this day, in the DOS library, and also in part, in the File System.

Since the day Commodore imploded, and a parade of owners and false starts basically condemned the Amiga to suffer from over a decade of abandonment, as far as operating system updates go, and support for the newer features that were desperately needed during this time.

Now, with a roadmap to follow once again, the Amiga OS is on the move to try and make up some ground for all those missing years of development.

However, as time has moved on, and the old 68000 CPU now in the realms of total obsolescence, and the hardware that supported the Amiga OS all those years, now unable to be considered in any way satisfactory for today's computing needs, the necessity to move the OS to new hardware base has become considerably urgent.

This is where OS4.0 comes in.

Not only do we need to catch up, but to do this the Amiga OS has to be "unhitched" from the old hardware base to do it, but obstacles being what they are, nothing is ever as easy as it seems, and this "unhitching" is also complicated by the fact that the vast majority of the OS source code was still written in MC68000 assembly code, which is CPU specific and in no way portable with any other sort of modern day microprocessors.

So, the first steps required that the larger parts of the OS had to be completely re-written in C.

Over the years, various parts of the OS had been updated and rewritten either completely, or at least in part, into C language, but due to the ancient origin of the DOS library, and the importance it has with application compatibility, it had remained in more or less the same state as it was from the end of the Commodore era, although, near the end, there were substantial features added and serious attempts to remove parts of the early TRIPOS layer.

Unfortunately, it never completely happened, and even with the last OS update, the early BCPL TRIPOS kernel still remained active & functional, but hidden underneath the higher layer that we are all familiar with and use every day.

To accomplish the goal of having a portable version of dos.library, the ancient TRIPOS kernel remnants had to go, mainly due to the way it was written and worked, it was unable to be duplicated in modern C language, it also required an environment that was substantially undocumented and now rarely used in any application software anyway.

So, the first job was to "unhook" the modern layer from the TRIPOS remains. This was not as easy as first expected and took me nearly 9 months to chip away at the hooks and ties that the modern layer had into it.

At each stage, something broke somewhere, be it in some of the handlers, or any number of other system components that took advantage of the old environment and/or side effects, a lot of these being things that would have never shown up even if you were looking for them. Trouble only appeared up when they had the rug pulled out from under them, even a lot of the C: commands still had many old TRIPOS code dependencies.

Thankfully, we have a great team of coders on this OS4 project, and as these dependencies were uncovered, they were soon fixed or rewritten in extremely short order, one by one.

Soon, all the old BCPL TRIPOS kernel dependant code was gone, and in the early morning of 07-December-2002, at 3am Queensland, Australia time, (just incase you really want to know exactly.) I booted up the first (TRIPOS free) Version 50 of dos.library, all the way to workbench.

Over the next few months or so, all the remaining assembly code "bits" were rewritten into C language.

At least in some way, nearly every programmer on the OS4 team has contributed to the new dos.library, be it by fixing other components affected by the changes, or, be it in dos.library itself, or even just ensuring application compatibility, by providing test cases.

Some outstanding work has been achieved by a number of contributors, many of whom I want to thank personally, because without their help, I doubt that I could have accomplished the task all on my own, at least not within several years, and, I don't need another day job.

Also, I don't want to forget to mention all our beta testers who are continuing to this day to uncover the odd bug or provide a lot of input into ways of improving the overall package, from a users perspective.

Here is a list of contributions from other programmers who supplied ready-made replacements for the V50 dos.library:

• Completely new replacement pattern matching routines.
• Completely new LoadSeg implementation.
• Completely new ReadArgs implementation.
• And many more new functions that are too numerous to mention here.

Also, the work on dos.library has not stopped at just porting it to C, but it has also undergone some much needed repairs and enhancements that have been required for many years, here is a (brief) list of new and enhanced features of the new V50 dos.library:

• The 255 bytes DOS "pathname" limits are now virtually gone.
• Many old bugs concerning NULL pointer passing are now fixed.
• Many more datestamp and time conversion functions are now available.
• New handler mounting routines are now built into dos.library.
• New address and segment tracking functions are now internal.
• Many more "task callable" DOS functions are now available.
• Enhanced error trapping and reporting for errant applications.
• Multi-Assign support for pattern matching functions.
• Built in support for PPC and other future formats.

During this development period, dos.library was being compiled with SASC compiler, but to port it to PPC, the GCC compiler needs to be used, and as of the start of May 2003, all the code was changed to work with GCC, and it functions rather nicely now.

All this work has been quite a chore, but I'm sure you will appreciate the effort that has gone into, not only dos.library, but all the other system components, and I'm sure you'll get to hear from some of the other programmers in depth regarding the work on their own modules, in the weeks to come.

So, to finish this article, and just for the dedicated readers here on CAM, I thought it might be nice to give all of you some memorabilia that no-one outside of the operating system programmers have probably never seen before. From V50 onwards, this has been consigned to the archive, forever.

The following text is from the original header in the old assembly language source code file from V40 DOS, named: "doslib.asm"

Enjoy !!!