In the series about MorphOS basics in the
MorphZone Library, I've written an extensive
article about taglists, one of main concepts of the AmigaOS (and its derivatives) API. Taglists were introduced in AmigaOS 2 and are present in almost unchanged form in MorphOS, AmigaOS 4 and also AROS, so it may be an interesting reading for developers working will all these systems.
