This chapter has notes about upgrading your application to Tcl 7.4 and Tk 4.0 from earlier versions of Tk such as Tk 3.6. This includes notable new features that you may want to take advantage of as well as things that need to be fixed because of incompatible changes.
Porting your scripts from any of the Tk version 3 releases is easy. Not that many things have changed. The sections in this chapter summarize what has changed in Tk 4.0 and what some of the new commands are.