Graphical displays in MGGHAT can be manipulated with a widget-based menu (but there are alternate ways to select graphical displays; see section 8.1). The widget-based menu is written in Tcl/Tk. Tcl is a ``tool command language''. Tk is an extension to Tcl that provides an interface to X Windows. wish is a simple windowing shell through which the Tcl/Tk program is run.
If you choose to use the widget-based menu for manipulating the graphical displays of MGGHAT , then you must have Tcl/Tk installed and wish in your executable path. If you do not use the widget-based menu, you do not need to have Tcl/Tk installed.
On some Linux systems, wish is called wishx. In this case, you should create a symbolic link from wish to wishx in a directory that is in your executable path.
If Tcl/Tk is not already installed on your system, the source codes for Tcl and Tk can be obtained by anonymous ftp from ftp.smli.com in the directory pub/tcl. You should get Tcl version 7.3 and Tk version 3.6.