This is an inexhaustive list of keyboard codes returned by GET and INKEY(x)
(where x >= 0).

Normal keys (and shifted keys) just return their ASCII values.
Key     Normal value    Shifted value   CTRL value      Shift-CTRL
PrtSc   128     &80     144     &90     160     &A0     176     &B0
F1      129     &81     145     &91     161     &A1     177     &B1
F2      130     &82     146     &92     162     &A2     178     &B2
F3      131     &83     147     &93     163     &A3     179     &B3
F4      132     &84     148     &94     164     &A4     180     &B4
F5      133     &85     149     &95     165     &A5     181     &B5
F6      134     &86     150     &96     166     &A6     182     &B6
F7      135     &87     151     &97     167     &A7     183     &B7
F8      136     &88     152     &98     168     &A8     184     &B8
F9      137     &89     153     &99     169     &A9     185     &B9
F10     202     &CA     218     &DA     234     &EA     250     &FA
F11     203     &CB     219     &DB     235     &EB     251     &FB
F12     204     &CC     220     &DC     236     &EC     252     &FC
Insert  205     &CD     221     &DD     237     &ED     253     &FD
Pause   196     &C4     196     &C4     244     &F4     244     &F4
Delete  127     &7F     215     &D7     231     &E7     247     &F7
Home     30     &1E     216     &D8     232     &E8     248     &F8
PgUp    159     &9F     143     &8F     191     &BF     175     &AF
PgDn    158     &9E     142     &8E     190     &BE     174     &AE

PrtSc is redefinable with *KEY0


The following keys change depending on *FX4 value.
*FX4,0 (and *FX4,2 if not redefined with *KEY):
Key     Normal value    Shifted value   CTRL value      Shift-CTRL
End     139     &8B     155     &9B     171     &AB     187     &BB
Left    140     &8C     156     &9C     172     &AC     188     &BC
Right   141     &8D     157     &9D     173     &AD     189     &BD
Down    142     &8E     158     &9E     174     &AE     190     &BE
Up      143     &8F     159     &9F     175     &AF     191     &BF

*FX4,1 (matches BBC Micro, End is mapped to Copy):
Key     Normal value
End     135     &87
Left    136     &88
Right   137     &89
Down    138     &8A
Up      139     &8B
Values with modifier keys are not changed by *FX4,1. On the BBC Micro and
Master, the modifier keys have no effect.
