Why does the Windows registry exist? [closed]

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this is more OS architecture question than programming directly, but still. Why was the Windows registry created as a completely separate subsystem for storing system/application settings? In *nix OS'es there is /etc directory which is perfectly understandable, as filesystem is a natural hierarchical way for storing settings, while Microsoft decided to create a completely outside hierarchical subsystem, which seems to be a foolish investment, why didn't they just use a filesystem hierarchy?

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1. Centralized - which is useful for roaming profiles.
2. Transactional - which makes it harder to smash your configuration.
3. Security - You can enforce read/write with better granularity than a file (per-key/value).

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So that when the binary registry gets corrupted, you'll just give up and go buy the newest version of windows for a fresh install.

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This article discusses INI files vs registry: https://devblogs.microsoft.com/oldnewthing/20071126-00/?p=24383.

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• Each application doesn't have to reinvent a config file format
• You can easily use the registry in kernel mode code

As mentioned in the Old New Thing article cited by Bastien:

• The system can handle concurrency issues for you
• You can ACL registry keys

I would also mention that many *nix frameworks have reinvented the registry... Like gconfd on GNOME.

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Also, file system granularity: one cluster for each value is a bit to much, so you need to make a tradeoff where the file system ends and the settings file starts. That of course doesn't give you a consistent API. So why not pull all settings into a few key files, and give you a consistent API to access it? BAM - registry.

(And since MS generally considers API more importantthan format, it's no surprise the files are opaque)

[Raymond Chen voice]Remember, it was designed for computers where 4MB of RAM was plenty.[/Raymond Chen voice]

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The idea is to have all settings for all programs stored in one single place instead of having them spread all over your disk.

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They did it, I believe, to support a separate setting for each login user. In Unix, there's a concept of home directory, while none in Windows.

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For starters, it's quicker to read and write to the registry during the course of a user session.

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It created a single point entry for the entire system's application configuration control. It would have been a nice usecase for an embedded network database (e.g. Raima used by Rational) or a text database (Bernstein's cdb).