By default, screen characters appear using simple ASCII key translations.
If desired, the application can set up alternate key mapping.  A pointer
to the KeyMap structure is placed into the AltKeyMap field of the
StringInfo structure.  The GACT_ALTKEYMAP bit in the Activation flags of
the gadget must also be set.

See the "Console Device" chapter in the Amiga ROM Kernel Reference Manual:
Devices, and the "Keymap Library" chapter in this manual for more
information about the console device and key mapping.