Assembling CP/M 3
=================

  The original CP/M 3 build process seems to have been written for a CP/M 3
computer; it uses the MAC, RMAC, LINK, GENCOM and HEXCOM tools, which are
not readily available for other platforms in this day and age.

  HEXCOM.C (based on LOAD.C in <ftp://oak.oakland.edu/pub/unix-c/> ) serves
as a suitable replacement for HEXCOM. The command syntax is:

  HEXCOM comfile <hexfile

  Similarly, to avoid a chicken-and-egg situation (SID is used to build SID),
HEXPAT.C has been supplied to overlay a COM file with a HEX file.

  The other tools are run under emulation rather than being ported. The
emulator in question is ZXCC (version 0.3 or later); this can be downloaded
from <http://www.seasip.demon.co.uk/Cpm/software/linux.html>. It will compile
under DOS with DJGPP.
  Note: Earlier versions of ZXCC cannot use LINK on programs bigger than 8k.
The latest ZXCC is necessary if you want to link the BDOS.

  ZXCC is _not_ a full CP/M emulator. It contains a subset of CP/M sufficient
to run the build tools above. Its command line syntax is:

  zxcc cpmfile {+}{-}arg1 {+}{-}arg2 ...

  The arguments arg1, arg2 etc. can be:

  filename    Arguments not starting "-" or "+-" are parsed as filenames.
             This process maps DOS directories to CP/M drives; so you could
             type ZXCC MAC.CPM G:\ASM\DUMP.ASM and DUMP.ASM would be visible
             to MAC.
 +filename    Arguments starting "+" are appended to the preceding argument.
             See the LINK example below.
 -text        Text starting "-" is copied in verbatim (not even converted to
             upper case).
+-text        The text is appended to the previous argument.

  The reason for the "+" options is: Filenames must be passed to ZXCC 
surrounded by spaces, but ZXCC may need to pass them to the program in the
middle of a string of text. In this example, ZXCC requires the filename parts
to be separated by spaces, but they must be passed to LINK as one word:

       LINK BDOS3=CPMBDOSX [OS,$SZ]

becomes

       ZXCC LINK.CPM BDOS3 +-= +CPMBDOSX -[OS,$SZ]
                           |   |
              +------------+---+
              |
The two + signs are used to remove the spaces either side of the "="; while
the "-" signs prevent the "=" and the "[OS,$SZ]" from being parsed as 
filenames.