Tk 4.1 is notable for its cross-platform support. Your Tk scripts can run on Windows, Macintosh, and UNIX. The associated Tcl release, 7.5, saw significant changes in event-driven I/O, network sockets, and multiple interpreters.
Cross-platform support, network sockets, multiple Tcl interpreters, and an enhanced
foreach command are the highlights of Tcl 7.5 and Tk 4.1.
Cross-platform support lets a Tcl/Tk script run unchanged on UNIX, Windows, and Macintosh. However, you can still have platform dependencies in your program. The most obvious dependency is if your script executes other programs or uses C-level extensions. These need to be ported for your script to continue to work.