I'm trying to pick up the D programming language, and I downloaded the compiler from the official site (http://www.digitalmars.com/d/download.html). and I'm following the original D programming tutorials and book. But the compiler doesn't seem to recognize a lot of keywords, for example when I try to use the "immutable" keyword the compiler raises the "Error: undefined identifier immutable" error. And it does this with a lot of other features of D.
How is this possible? It is in fact the official compiler as far as I know.
You downloaded the D1 compiler. Get the D2 one.