While this topic might be regarded as merely a special case of the more general topic of "[Extending Tcl]", many newcomers to the subject conceive it in these more mechanical terms. [[...]] Variations: * [Critcl] and so on * compiled-in [extension]s * "impedance-matching" loaders Among the latter, [Windows] variants include * [Yet another dll caller] * [ffidl] * [dllcaller] and, in a different way, * [COM] (in the broad sense, that is, including [OLE] and [DCOM]) * [DDE] [[Mention [SWIG].]]