[kccqzy]

I've also wanted to understand Windows NT at this depth for a while. Skip the Win32 stuff, and discuss what's underneath it. As I understand Win32 is just one personality; there was also Windows Services for UNIX in the Windows XP days and Subsystem for UNIX-based Applications in Windows Vista. The underlying NT kernel is flexible enough to allow POSIX compliance. That would be an interesting read.

[p_ing]

Windows Internals is the book you want.

Or Inside Windows NT, if you want "version 1" of the Internals series. Or read the Windows NT OS/2 Design Workbook - https://computernewb.com/~lily/files/Documents/NTDesignWorkb....

Yes, Win32 is just one personality, but a required one. OpenNT, Interix, SFU, SUA will ride alongside Win32. And of course there was the official OS/2 personality.

[nunez]

100%. Russinovich, who now heads up Azure, co-wrote many of the follow-on books, and David Solomon, who co-wrote the NT kernel, co-wrote the first few. The latest version of this book covers Windows 10/Server 2016. They are very, very good.

[skissane]

> As I understand Win32 is just one personality

Not really... although NT was designed to run multiple "personalities" (or "environment subsystems" to use the official term), relatively early in its development they decided to make Win32 the "primary" environment subsystem, with the result that the other two subsystems (OS/2 and POSIX) ended up relying on Win32 for essential system services.

I think this multiple personalities thing was the original vision but it never really took off in the way its original architects intended – although there used to be OS/2 and POSIX subsystems, Microsoft never put a great deal of effort into them, and now them are both dead, so Win32 is the only environment subsystem left.

Yes, there is WSL, but: WSL1 is not an environment subsystem in the classic NT sense – it has a radically different implementation from the old OS/2 and POSIX subsystems, a "picoprocess provider". And WSL2 is just a Linux virtual machine.

[ForOldHack]

"At the same time, NT (up to and including Windows 2000) shipped with an OS/2 subsystem which ran character-mode 16-bit OS/2 applications." From OS/2 museum.

[ForOldHack]

Turns out this is not true. Confirmed that os/2 2.0 was a skinning and compatibility layer for NT it came out for OS/2, not with windows and not from Microsoft. It came with OS/2 and from IBM. No idea whether it supported HPFS+ but it was not a subsystem.

[skissane]

> Turns out this is not true.

No, what you quoted in your comment you are replying to is accurate. What you are saying in this comment isn’t.

> Confirmed that os/2 2.0 was a skinning and compatibility layer for NT it came out for OS/2,

This is confused. OS/2 was not a “skinning and compatibility layer for NT” it was a completely separate operating system.

I think at one point NT was going to be OS/2 2.0, and then it was going to be OS/2 3.0 - but the OS/2 2.0 which eventually ended up shipping had nothing to do with NT, it was IBM’s independent work, in which Microsoft was uninvolved (except maybe in its early stages).

[ForOldHack]

WSL2 is just a Linux VM, and the POSIX subsystem is just a kluge I never heard of an OS/2 subsystem for NT, for which Cutler would take extreme umbridge in.

I have three charts on my wall( now 4): the Unix timeline, the windows timeline, and the Linux distribution tree,and now a very decent MacOS X timeline.

The personalities became containers which is just the windows version of common subsystem virtualization. Containers were based on VirtualPC, but with the genius of Mark Russinivich.

[skissane]

> I never heard of an OS/2 subsystem for NT,

It was there from NT 3.1 until Windows 2000; it was removed in Windows XP onwards.

It was very limited – it only supported character mode 16-bit OS/2 1.x applications. 32-bit apps, which IBM introduced with OS/2 2.0, were never supported. Microsoft offered an extra cost add-on called "Microsoft OS/2 Presentation Manager For Windows NT" aka "Windows NT Add-On Subsystem for Presentation Manager", which added support for GUI apps (but still only 16-bit OS/2 1.x apps) – which was available for NT version 3.1 thru 4.0, I don't believe it was offered for Windows 2000.

The main reason why it existed – OS/2 1.x was jointly developed by IBM and Microsoft, with both having the right to sell it – so some business customers bought Microsoft OS/2 and then used it as the basis for their business applications – when Microsoft decided to replace Microsoft OS/2 with Windows NT, they needed to provide these customers with backward compatibility and an upgrade path, lest they jump ship to IBM OS/2 instead. But Microsoft never tried to support 32-bit OS/2, since Microsoft never sold it, and given their "divorce" with IBM they didn't have the rights to ship it (possibly they might have retained rights to some early in-development version of OS/2 2.0 from before the breakup, but definitely not the final shipped OS/2 2.0 version) – the OS/2 subsystem wasn't some completely from-scratch emulation layer, it was actually based off the OS/2 code, with the lower levels rewritten to run under Windows NT, but higher level components included OS/2 code largely unchanged.

> for which Cutler would take extreme umbridge in.

Windows NT was originally called NT OS/2, because it was originally going to be Microsoft OS/2 3.0. Part way through development – but at which point Cutler and his team had already got the basics of the OS up and running on Microsoft Jazz workstations (in-house Microsoft workstation design using Intel i860 RISC CPUs) – Microsoft and IBM had a falling out and there was a change of strategy, instead of NT providing a 32-bit OS/2 API, they'd extend the 16-bit Windows 3.x API to 32-bit and use that. So I doubt Cutler would take "extreme umbrage" at something which was the plan at the time he was hired, and remained the plan through the first year or two of NT's development.

> The personalities became containers which is just the windows version of common subsystem virtualization.

Containers and virtualization are (at least somewhat) successors to personalities / environment subsystems in terms of the purpose they serve – but in terms of the actual implementation architecture, they are completely different.

[pjmlp]

Windows containers are built on top of jobs infrastructure.

https://learn.microsoft.com/en-us/virtualization/windowscont...

https://learn.microsoft.com/en-us/windows/win32/procthread/j...

[skissane]

> running on Microsoft Jazz workstations (in-house Microsoft workstation design using Intel i860 RISC CPUs)

Correcting myself: Microsoft Jazz machines used MIPS not i860; the i860 machines were Microsoft Dazzle

NT for MIPS actually ended up shipping for customers; I believe NT for i860 was abandoned as soon as the MIPS port was usable

[p_ing]

> 32-bit apps, which IBM introduced with OS/2 2.0, were never supported.

This was obviously due to the divorce, but also that the Cruiser API wasn't finalized.

> Our initial OS/2 API set centers around the evolving 32-bit Cruiser, or OS/2 2.0 API set. (The design of Cruiser APIs is being done in parallel with the NT OS/2 design.)

...

> Given the nature of OS/2 design (the joint development agreement), we have had little success in influencing the design of the 2.0 APIs so that they are portable and reasonable to implement on non-x86 systems.

[skissane]

I’d love to read the document you are quoting - is it publicly available anywhere?

[p_ing]

Yep - https://computernewb.com/~lily/files/Documents/NTDesignWorkb...