Architecture of Windows 10 and Windows 11

Windows 10 architecture is not a needle in this haystack.

One of the reasons why so many developers do not understand how the Windows Runtime works (other than looking into its documentation strangely sparse and overwhelming at the same time) is not just because the tooling and language “projections” obscure the underlying platform. No. The real reason is: there are no clear and detailed Windows 10 blueprints.

In other words: There is no officially supported, published, and reviewed, Windows 10 and Windows 11, detailed architecture available.

(In case you think you are in the wrong post perhaps you might want to escape in the direction of development)

Why Architecture?

So who cares about this Architecture “thing” anyway? The simple answer is: you, the software developer, should care. Architecture is imposed on you. You do suffer (for many years) or (who knows) possibly enjoy Windows Architects’ decisions.

There is an example: it turns out that for some reason inheritance has been chosen (by Architects) over aggregation in WIN10  RT API and especially so in its implementation patterns. And then, at the same time, while learning WIN RT API, one is faced with effectively not having interface inheritance in a new IDL.  Curious and peculiar. The question is: Why?

Well, some Windows 10 Architect (I hope) knows why. But who she is? Where are they? Who do you call for real fundamental and necessary details, if you want to really understand Windows 10 API?

Good Architecture tells us WHY has something been done. Not HOW and not WHEN and not WHO …

“How” might be answered by a technical or application Architect. But that is way below the top-level Windows 10 System Architecture we are talking about here. Technical/Application Architect is more of an organizational tag for an important role of a senior developer.

Channel 9?

“Channel 9” is full of Architecture. Will it help perhaps, to follow all those Architects over there? Perhaps it will. But none of them clever MSFT Architects, never ever really answers that proverbial “Why” question. Although, as a matter of fact, nobody is asking them. Especially not on Channel 9. And that is funny.

Microsoft Docs?

OK then, who else can help and is now over there sailing on the surface of the Microsoft Docs ocean? There are indeed guys (possibly called Application Architects) who can show you how actually WIN RT API works. In great detail, too. How COM is back into the limelight, and HOW C# now understands WIN RT components written in modern C++. As a good example, Kenny Kerr is a rather insightful and talented guy. But Kenny just delivers the HOW. Kenny never asks or answers WHY.

Why is Architecture important?

Because (among a few other reasons) Architectural decisions are impossible to change after the implementation milestone has been reached. Which makes them very important. And in case of mistakes, very (very) expensive.

Paradoxically non-existence of Architectural decisions is one fact impossible to change. And neither of the two (decisions or lack of) is good information to publish. Especially not good for shareholders and the company’s income.

Existence of Architecture is important, but non existence of Architecture is even more important

How so?  Here is one example. Windows “zero” was (it seems somewhat) quickly built as an MS-DOS add-on. Built. Not Architect-ed, designed, built, tested, and then again to cycle 2 and the next cycle and so on. The fact that WIN 0.x was never Architect-ed is one fact almost impossible to deny. During the last 30+ years, I do not remember anyone who has ever tried to deny this. So After 30+ years, I will call it a fact.

Thus it is very hard to defend against the claim that Windows 1.0 has generated one enormous technical debt.  Therefore. Publishing Windows 10 (or whichever) blueprints right now might actually break Microsoft Inc. How?

Remember this is not a source code we are talking about here. We are talking about Windows 10 System Architecture. Detailed OS Architecture is a blueprint, not a source code. A skyscraper is built by producing (very) detailed blueprints, finished before the actual building is built 1.

The existence of Window’s detailed architecture published will allow experts to quickly reveal the weak points. With the dates. The nightmare details. Inherited all the way back from Windows 0. x.

The speculations from the last 30+ years (if that revelation ever happens) will quickly transform into facts. People will be able to see there was no Architecture BEFORE Windows 1.0 was ever built. In a way, Windows is one huge multi-decade-long struggle for hundreds (thousands ?) of good developers. And many  (many) more architects and developers know that. But.

There is no detailed published Architecture available and all is just (carefully kept) as one big speculation. We all know they (MSFT developers) are working hard and they are working for years, on each new Windows release. But nobody is telling us, what exactly seems to be the problem, and most importantly why. It is impossible to argue, without Architectural blueprints. No blueprints no discussion.

Why COM (again)?

Based on this swampy, erratic, shifting grounds is the “tower of” COM. Besides WIN NT, COM is one huge achievement in the long history of Windows struggle. Let me put it into perspective for you: COM is like a deep-sea oil rig that has never been broken. Something that is virtually unheard of. And crucially:  each deep-sea oil rig improvement always starts by revisiting its architecture. One luxury that (I assume) COM architects had.

COM is one Windows subsystem we know a lot about, and into which we implicitly trust, because Microsoft obviously trusts COM. We know a lot about COM, but (again) we do not know: WHY. There are no COM blueprints published. No detailed COM System Architecture.

COM “material” is thus a good example of how very carefully Windows Architecture bits and pieces are sanitized and then released into the “wild”.


Perhaps some of my older audience remembers Tanenbaum and his “MINIX” OS. In mid last century, people realized computers might become personal. Academia got interested in the challenge and has produced  OS-es to utilize those little personal computers. People discussed them, architect-ed them OS-es, and so on.

That has greatly influenced one young Linus Torvalds who has afterward developed LINUX.  This is how software systems and especially the most complex ones called “operating systems” are and should be developed. Architecture-driven, developers built.

And what about Windows? There is no Academic proof of the quality or correctness of WIN Architecture because there is no WIN Architecture to see. It was never published. We know a lot of high-level details about Windows. But almost nothing below that. Going further down will be reverse engineering. The ultimate (and punishable) NO NO.

But (besides LINUX variants) there are a few more OS-es, on the market today. Do we know more about them? We do not. Make no mistake:

No modern, commercial OS will have it’s detailed Architecture published.

And here I mean OS System Architecture. Not marketing leaflets block diagrams called “architecture”. It is just too dangerous to publish such a thing called Detailed OS Architecture. Thus, around commercial modern OS-es, there is a lot of deliberate speculation and FUD. Things are happening out of the blue. Or not happening? And we can just speculate WHY. No blueprints no discussion.

Windows 10 and 11 Architecture?

I have seen WIN10 and WIN11 and I am using them right now. WIN10/11 “feels” to me as an  OS well architect-ed. I can “feel” it is quicker than its predecessors working inside the same VM with the same amount of RAM and same sized HD, and the same underlying host hardware.  But, I am an Architect and I should be able to objectively quantify this subjective opinion of mine. And, I will. Here it is.

OS Architecture is the biggest crown jewel in every software company’s crown. But there is much more to it. Architecture is not to be sold and it is not ever to be seen. Ever. OS Architecture is the gemstone of great magical power. The power is lost as soon as the stone is seen.

A rather quantum situation: we know it is there and we know it is fundamental. But we can not directly observe it.

That is the real technical explanation for you, on what is OS Architecture today. Windows 10 and Windows 11 including.

1:  Software is not built from brick and mortar and is thus much easier to bend this simple rule: First Architect, then design, and then build. Bend in the context of software development cycling. True, but, never without skipping any of the three phases. Never. This (we can only speculate) was exactly the case with Windows 0.x: Architecture was skipped, in those primordial days of Windows.

Architecture can not be glanced over.
Architecture can not be “glanced” over.

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