incr Tcl adds object-oriented programming facilities to Tcl. It was NOT designed as yet another whiz-bang object-oriented programming language; indeed, it is patterned somewhat after C++. It was designed to support more structured programming in Tcl. Scripts that grow beyond a few thousand lines become extremely difficult to maintain. [incr Tcl] attacks this problem in the same way that any object- oriented programming language would, by providing mechanisms for data encapsulation behind well-defined interfaces.
Please read the file /usr/doc/packages/itcl/README.SuSE.