BBC MOS 0.xx Keymapping
                                     =======================

+==+====+====+====+====+====+====+====+=====+=====+=====+=====+=====+=====+=====+=====+=====+
|  | x0 | x1 | x2 | x3 | x4 | x5 | x6 | x7  | x8  | x9  | xA  | xB  | xC  | xD  | xE  | xF  |
+==+====+====+====+====+====+====+====+=====+=====+=====+=====+=====+=====+=====+=====+=====+
|0x|    |    |    |    |    |    |    |     |     | Tab |     |     |     |Retrn|     |     |
+--+----+----+----+----+----+----+----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
|1x|    |    |    |    |    |    |    |     |     |     |     | Esc |     |     |     |     |
+--+----+----+----+----+----+----+----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
+--+----+----+----+----+----+----+----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
|7x|    |    |    |    |    |    |    |     |     |     |     |     |     |     |     | Del |
+--+----+----+----+----+----+----+----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
|8x|    |    |    |    |    |    |    |Copy | <-  | ->  | Dn  | Up  |     |     |     |     |
+--+----+----+----+----+----+----+----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
|9x| f0 | f1 | f2 | f3 | f4 | f5 | f6 |  f7 |  f8 |  f9 |Break|     |     |     |     |     |
+--+----+----+----+----+----+----+----+-----+-----+-----+-----+-----+-----+-----+-----+-----+

The base and number of soft keys can be changed by setting internal variables. By default the
keyboard driver treats all &9x as soft keys.