I was reading an article about how to use the sizeof operator in C#.
They say: "Used to obtain the size in bytes for an unmanaged type."
I know the difference between managed and unmanaged code. But my understanding is that all code I write in C# (including all predefined and user-defined types) is managed by the CLR. So what do they mean by "unmanaged types"?
The term "unmanaged type" is a little bit misleading: is not a type which is defined in unmanaged code. It's rather a type which doesn't contain references managed by the garbage collector.
In C# 7.3 there is even a generic constraint unmanaged:
[...] must not be a reference type and must not contain any reference type members at any level of nesting.
If you have experience with WinAPI: the originally proposed name for unmanaged types was blittable.