Lesson 15

 Frames - in tkinter -  are very easy to code but they play an absoluterly

essential role: that of keeping widgets close to each other. 

Consider: had we just disposed our buttons with the pack() function, 

then making the window larger would move the buttons apart, TOP, Bottom...

whatever, like contiments drifting apart on the globe. A frame container makes 

everything move together.

One is then free to place the container where one wants it in the window, here at

(100, 100)

Another festure of the code: the syntax for coding the buttons is simplified:

all on one line, with frame as the 'master' for the widget rather than window.