Code Words

Code words are the most primitives words in gbforth, and are defined in assembler. The core library contains a lot of these primitives already, but sometimes you may need to write new code words yourself.

You can define new code words using the code and end-code word. For example, c@ can be defined as follows:

( c-addr -- c )
code c@
  [HL] L ld,  \ HL register contains TOS
  $0 # H ld,  \ clear the higher byte
end-code

When defining new code words, keep the memory and register allocations for the kernel in mind. Overwriting values in reserved registers (without restoring them properly) might lead to unexpected behaviour.