QDOS Internals

Anything you never knew you wanted to know about the Sinclair QL.

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Assembly Language Mailing List

With the demise of the last surviving QL magazine in print form, QL Today, my series on Assembly Language came to an abrupt end. I still dabble in Assembly Language and some of my faithful readers might wish to keep up to date with my various ramblings on the matter. If so, please subscribe to my mailing list so that you can be kept up to date as and when I create new articles. I have to say though, I'm pretty intermittent in getting stuff ready to "print", so there is no fixed schedule for when the next issue will be made available.

I also had plans to combine everything done so far over the years into a "book" and make that available for download too. That work has been completed and the latest copy can always be downloaded from https://github.com/NormanDunbar/QLAssemblyLanguageBook/releases/latest. Enjoy.

You can subscribe to the mailing list at http://qdosmsq.dunbar-it.co.uk/mailinglist. Please note, that I ask for your name as part of the subscription process, this is to try and stop spam bots from subscribing. I get a lot of those. I do not use your information for any other purpose than sending out notifications about the eMagazine.

Registering for Write Access

Due to spammers, I have had to disable self-registration of new users on this site. If you wish to contribute, see Registration below for details of how you can register.

To save you hunting down the links to the actual content of the site, I'm putting them here at the top where it is easy to find.

These are links to specific topics about the Wiki itself, not its contents.

And finally, charitable stuff you may be interested in taking a quick look at and possibly helping people less well off that we are. Or indeed, chickens!

My Book


In April 2020, after over two years in the making, my first book was published by APress. Ardiuino Software Internals explains all about the Arduino Software, and "language" and how it works. Also, the book connects the software to the hardware by showing you how the hardware works.

You can find it on the Apress web site at https://www.apress.com/gb/book/9781484257890, on Amazon (UK) at https://www.amazon.co.uk/Arduino-Software-Internals-Complete-Language/dp/1484257898 or on Amazon (USA) at https://www.amazon.com/Arduino-Software-Internals-Complete-Language/dp/1484257898. Usually Apress (aka Springer) has a better price and free world wide postage. Amazon may have a cheaper price from time to time, but if it gets below £20.00, they will charge you for postage.

The book is 600 pages plus the index. I think it's an excellent book, but don't take my word for it, there's a review over on youTube at https://www.youtube.com/watch?v=lF2v47PNCDU&t=505s. Have a listen, then make your own mind up.

If you buy, or have already bought, a copy, thank you very much.

If you didn't, or haven't bought a copy – why not? :-(

If you can't make up your mind, try Amazon's "look inside" option and grab a preview; or, alternatively…

Look for the Kindle version on Amazon and download a free preview.

If you are interested, this is the blurb on the back cover:

It’s not enough to just build your Arduino projects; it’s time to actually learn how things work! This book will take you through not only how to use the Arduino software and hardware, but more importantly show you how it all works and how the software relates to the hardware.

Arduino Software Internals takes a detailed dive into the Arduino environment. We’ll cover the Arduino language, hardware features, and how makers can finally ease themselves away from the hand holding of the Arduino environment and move towards coding in plain AVR C++ and talk to the microcontroller in its native language.

What You’ll Learn:

  • How the Arduino Language interfaces with the hardware, as well as how it actually works in C++;
  • How the compilation system works, and how kit can be altered to suit personal requirements;
  • A small amount of AVR Assembly Language;
  • Exactly how to set up and use the various hardware features of the AVR without needing to try and decode the data sheets – which are often bug ridden and unclear;
  • Alternatives to the Arduino IDE which might give them a better workflow;
  • How to build their own Arduino clone from scratch.

Who This Book Is For:

No expertise is required for this book! All you need is an interest in learning about what you’re making with Arduinos and how they work. This book is also useful for those looking to understand the AVR microcontroller used in the Arduino boards. In other words, all Makers are welcome!

The Other QL Wiki

This is not the only QL Wiki in the entire world. Rich Mellor has one with lots of information on the QL in general, some of the characters and software available - past and present. The link is http://qlwiki.qlforum.co.uk. Check it out, and why not contribute a page or two?


Welcome to QDOSMSQ.Dunbar-it.co.uk the new home of the web site formerly known as QDOS Internals.

This website intends to be the definitive on-line location for all known information about the internal workings of the QDOS and SMSQ/E operating systems for the good old Sinclair QL Computer and derivatives.

The site is able to be read by anyone but only updated by registered users.

Thanks George

I started a web site many years ago. It was called QDOS Internals and on it I started to document everything I knew or could find out about the inner workings of QDOS. That web site underwent long periods of not much happening at all as work and 'life' took up most of my waking hours.

I converted the web site to a Wiki - you are reading it now - and opened it up to all and sundry after I had converted a fair amount of the old HTML pages to the text format used by the Wiki.

However, one of my registered users has excelled at writing documentation and has filled many pages on this Wiki. That user is George Gwilt and I would like to publicly thank him for helping out with the documentation.

Hopefully more users will add to the site and indeed, I hope to get time to add a lot more myself as well. I don't intend to leave everything to George to write for me!



Registration has been disabled . As of first April 2013, registration has been disabled on this web site, there is no longer a link on the login page to allow you to register.

You can still read the pages without registering, but only registered users can contribute or update the site.

This unfortunately had to be done as I came under attack from a bot of some kind, which simply kept on registering new users in a loop. This used up all my bandwidth and disk space allowance.

If you wish to register, email me at on the QL Users list and I'll set up a username and a default password for you. Once you login, you can change the password to something secure!

Cheers, Norm.

Charitable Stuff

The following are links to charities that myself and my wife, support. Please feel free to visit and maybe make a donation. Thanks.

Enter the QDOS/SMSQ Site

Click here to enter the site. Alternatively, click on the Qdosmsq link in the contents panel to the left of the page. You can also click on the 'QL' image littered about this page! Click here to enter QDOSMSQ ....

Read my blog

I have a blog now - like most of the rest of the on-line world. You can join in the fun by clicking here if you wish to.

It is not QDOSMSQ specific, you'll find lots of stuff there eventually. Some of it wholesome, some of it offensive. I can rant on almost any subject for quite some time when the mood takes me. Sometimes I'm even right!

Linux Musings and Ramblings

I quite like Linux, I certainly prefer it to Windows that's for sure. To this end and especially after Windows ate my Linux root partition just after Christmas 2007, I decided that my Laptop would be totally Linux - and so it is. It is now running Linux Mint and in my opinion, this is the finest version of Linux yet, especially for any first time converts from Windows.

The one program I did use under Windows, QPC2, runs perfectly under Linux with Wine, however, it cannot access QDOS floppy discs natively - not a problem for me these days as all my old QL floppies died a horrible death in storage. Under Windows it uses direct sector access (I'm told this by Marcel) which is not going to work on Linux under Wine. What to do? The sole survivors of my floppy collection have been "ripped" to image files on Linux using the dd command, and QPC is able to read those images as if they were floppy drives.

Enter the Linux Site

Click here to enter the Linux portion of my Web site. Alternatively, click on the Linux link in the contents panel to the left of the page. I'm not saying it will be pretty inside, but hey, these are the ramblings of a mad man! LOL

Click to enter Linux site...

start.txt · Last modified: 2021/12/13 16:13 by normandunbar