29 февраля 1996

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*  PART 7  - TECHNICAL FORUM  *
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TECHNICAL WRITES

Although  nobody  has  sent  me  a message
about    this   query,   a   friend,   who
occasionally   reads  this  magazine,  has
asked     for     an     explanation    of
"hand-blocking",  a  method sometimes used
to transfer old games to different media.

Basically, it works like this:

1.  Use  a tape header reader to determine
the  start  line of the first BASIC block,
and  the  addresses  and  lengths of other
blocks.

2.  Reset the computer and MERGE the BASIC
loader.  After a pause, it should give OK.
Programs larger than 7K may cause a system
crash  if they have been made MERGE proof.
It  should also be noted that all auto-run
programs on Microdrives are MERGE proof.

3.  Edit  the LOAD statements so that they
access  the  new  device  rather  than the
tape,  including filenames. If a screen is
loaded by LOAD ""CODE, change this to LOAD
*"m";1;"filename"SCREEN$      (or     LOAD
"a:filename"SCREEN$,   or   whatever  your
device  needs).  Any  block  which  passes
through  any  of  the  addresses  23672 to
23674  needs its start address added after
CODE.

4.  SAVE  the  loader  to  the new medium.
Remember the LINE parameter.

5.  Reset the computer. Except for screens
and  blocks  which  pass  through 23672 to
23674,   LOAD   further  blocks  to  their
original  addresses,  and SAVE them to the
new medium from those addresses with their
original  lengths.  Remember  to CLEAR one
byte below the start address first, unless
the  bytes load to the system variables or
printer buffer.

6.  Screens and frame-count-protect blocks
(those  which  affect 23672 to 23674) need
their   contents  preserved.  CLEAR  32767
(25855  on  a  16K)  and LOAD the block to
32768  (25856  on 16K). SAVE it to the new
medium  from  32768  (or  25856)  with its
original length.

7.  When  all  blocks are completed, reset
the  computer and LOAD the loader from the
new   medium.   The   game   should  start
normally.

Technical  editor,  Phil  Reynolds, can be
contacted by e-mail:
phil@hedgford.demon.co.uk,        or faxed
(+44/0) 1543 428082.

Technical queries will usually be answered
in the next issue of Emulate.

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