Where is the tcltk package? --- Summary

Summary of what I've learned:

(1) The tcltk package ***comes with R***; one does not install it from CRAN.

(2) In order for it to work, you need to have the *development* version of
tcltk installed on your system.

(3) Under Ubuntu Linux you can obtain the aforesaid development version by:

     sudo apt-get install tcl8.5-dev tk8.5-dev

(I still don't know what one does if that number 8.5 changes --- as new
releases come about.  How does one find out the number of the latest
release of tcl/tk?)

I hope that this may be of use to someone in the future.

     cheers,

         Rolf Turner

P. S.  Another thing I learned over the course of this inquiry is that I can
get the binary of R for Ubuntu (and save a bit of time and effort over
the process of installing from source) via

     sudo apt-get install r-base r-base-dev


         R. T.