TCDesktop consists of a series of macros that makes it possible to compile and link TransCAD's GISDK scripts on the fly. TCDesktop is also a complete menu system for running your TransCAD based travel demand model and a set of GISDK scripts which implement most standard travel demand modeling tasks. (TCDesktop was developed and is marketed jointly with the Transportation Business Group of CH2M HILL Engineers).
The links below provide some more detail regarding TCDesktop and how it works.