ITC stands for ’Interactive Todd Coxeter’. The package provides a program that allows you to execute interactively single steps in an enumeration of the cosets of a subgroup of a finitely presented group using the graphics surface XGAP of GAP and thus to see in various windows exactly what is happening. Note that the ITC package cannot be loaded from GAP, but only from XGAP. Hence it requires the XGAP package.