🚀 go-pugleaf

In article <161@vger.UUCP> valencia@vger.UUCP writes:
>
>	I've just finished writing a multi-tasking FORTH for the Z-80.
>Like so many before, I held off on the disk drivers until the system
>was more or less debugged. Then I came across what ends up being an
>interesting question in FORTH philosophy: exactly how DOES one do the
>FORTH memory buffering scheme? [...]
>					Andy Valencia


I have a Z80 multiuser Forth, based on NVSS F83 Forth.  This and every other
multitasking Forth I have seen (including polyFORTH) will only change tasks
when a word PAUSE is executed.  All I/O and disk accessing words contain
PAUSE, especially in any ready-wait loops.  Essentually this means that the
address returned by the BLOCK word is valid until the next I/O word.  It is
the task's responsibility to move any data to a private storage area if it
needs to do I/O without possibly loosing the data.  The word ">TYPE" is used
in the words LIST INDEX, and within the editor to make sure an entire line
of a screen gets printed before the buffer gets swapped out.  It is defined: 
  : >TYPE SWAP OVER PAD SWAP CMOVE  PAD SWAP TYPE ;
(it moves the data to PAD before typing). 

Two block buffers are adequate.  If operating under a DOS, such that the
block buffers are associated with files, there are additional complications
is different tasks can refer to different files.

Tom Almy