Tk is an interface toolkit that provides widgets in the Motif(TM) style, but built on top of Xt. Since no Motif license is required, Tk runs on freeware systems such as Linux and FreeBSD, and on non-X11 systems such as Windows(TM) and the Macintosh® computer. Extended Tk, or TkX, provides access to functional extensions in TclX.
Tm, or Tcl Motif, is an interface toolkit that provides access to real Motif widgets. The results you can obtain with Tm are often far superior to those obtainable with Tk.
If you base an application on SGITCL and Tk or Tm, you can modify both the program's functionality and its user interface at run time by writing or changing short Tcl scripts. Many new applications can be created without writing any C code at all, just by writing short scripts for wishx (windowing shell for TkX) or moat (Motif Tcl shell).
Control of remote systems is possible using the expect program.
SGITCL is a bundled product in IRIX(TM) 6.2. It includes TclX, TkX, Tm, and many other frequently requested Tcl extensions. Chapter 2 describes the commonly available Tcl extensions. Chapter 3 describes extensions that are exclusive to the IRIX system.