Sound and Keyboard now working

I've now got the sound and keyboard working - except for a few tweaks (the emulator still always loads a file called 'test.bin') it is essentially complete.

There will always be a few bugs. I found that (for example) the assembler was compiling TKA as $0B rather than $08 which caused some chaos, as $08 (COMC) is the command to switch to the upper 1k of ROM (sort of).

But hopeful I will release the source later today or early tomorrow - I'll set up XP in a VirtualBox machine and build a DOS version as well, because it's built for a Mac.