> SQL Server is a fork of Sybase. Not a MS invention.
It's long-since been rewritten. Pre-SQL Server 2000 it was garbage, but it's been improved significantly since then. I'd still use alternatives given the choice, but it's a solid DB.
>Active Directory is probably based on someone's LDAP server, though I don't know for sure.
So you don't know. It was written in house, using a bunch of standardized protocols (LDAP, X.500, kerberos), though with proprietary extensions (GPOs, etc).
> .NET is a copy of Java
That's a gross oversimplification. It's arguably a rip-off after MS tried to sabotage java, but it's their own implementation.
> NT kernel is good, thank Digital/Dave Cutler for that.
Yes, MS hired an experienced OS person for it. Probably one of the best things they ever did.
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I'm not saying MS deserves kudos or the benefit of the doubt, but they can put out good software, and these are all mission-critical examples of what they have to (having AD go down would bring a whole corporation to a halt). The problem is that with almost everything else, MS has the incentive and capability to ruin. And ruin they do...
For early history about Active Directory, you can't get much better than straight from the horse's mouth ( manager of the Exchange / Active Directory group ).
see https://hardcoresoftware.learningbyshipping.com/p/021-expand...
and
https://hardcoresoftware.learningbyshipping.com/p/bonus-the-...
I will say that in the era when they came out with AD they really took "enterprise configuration management" seriously and made Windows by far the best mainstream ecosystem to manage hundreds or thousands of corporate desktops.