ftp.barnyard.co.uk/2015.02.ftp.barnyard.co.uk.tar/ftp.barnyard.co.uk/cpm/walnut-creek-CDROM/BEEHIVE/UTILITYS/CORK10.ARC/CORK.DOC

Text File | 1991-08-11 | 10KB | 179 lines

   [Enter Andy Roony]

   Did you ever call a *DOS BOARD* with a *CP/M MACHINE* and get screen
   full of *GIBBERISH* that looked something like *THIS*?:


   ZZDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD??
   33 NEW DOORS AND AN RLE CONFERENCE HAVE BEEN SET UP.... 33
   @@DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDYY
                            ZZDDDDDDDDDDDDDDDDDDD?DD??
   ZDOOR......              33TRY THEM OUT.......3  33    ZDOOR...
      BATCH transfers       @@DDDDDDDDDDDDDDDDDDDYDDYY
   ZZDDDDDDDDDDDDDDDDDDDD??DD????DD??
   33THEY NEED USER INPUT33  3333  33  ADVENTURES!!! *   -QWIKMAIL>>>>>
   @@DDDDDDDDDDDDDDDDDDDDYYDDYYYYDDYY

   [Exit A.R]

   Well, those screens look OK with the IBM extended character set, but
   what about the rest of us?  Well, no miracles, but surely the situa-
   tion could be improved somewhat:

   ++------------------------------------------------------++
   || NEW DOORS AND AN RLE CONFERENCE HAVE BEEN SET UP.... ||
   ++------------------------------------------------------++
                            ++-------------------+--++
   ZDOOR......              ||TRY THEM OUT.......|  ||    ZDOOR...
      BATCH transfers       ++-------------------+--++
   ++--------------------++--++++--++
   ||THEY NEED USER INPUT||  ||||  ||  ADVENTURES!!! *   -QWIKMAIL>>>>>
   ++--------------------++--++++--++


   ----
   Those  aren't  really "D"'s, etc. coming thru in  the  first  example-
   they just appear that way after stripping the valuable 8th bit identi-
   fying  it as a deviant graphic character.  Contained herein is a  tiny
   (1/2k) program that will sit in the top of your memory and remap these
   characters into more useful ones.  It turns out that a fairly  aesthe-
   tic  approximation  of the originally desired effect can  be  achieved
   with  a combination of only three standard characters: "-",  "|",  and
   "+".  As supplied, the program does exactly such an remapping of char-
   acters.  All codes intercepted with values higher than 128 decimal are
   instantly remapped into an appropriate substitute, in real time.

   The  RUN-DMC, uh, RUN-ZMP program provided will quietly locate  itself
   in high memory and then automatically load the ZMP modem program  (the
   specifics can be changed, as described later).  You may then call  DOS
   boards   and  enjoy  a  much,  er,  somewhat   healthier   experience.
   [Note: You must configure ZMP *not* to remove the parity bit for  this
   to work.  This is done by setting the (P)arity selection to NO in  the
   (S)ystem  submenu of the (C)onfiguration menu]. Fortunately,  ZMP  has
   this option and it thus works quite nicely with this program.

   In  theory,  the concept can be extended to work with MEX  or  IMP  as
   well.  Unfortunately, experiments seem to indicate that both of  those
   communication  programs  strip the high bit before sending it  to  the
   console,  regardless of the setting of the their  respective  'control
   character filter' switches, so someone will have to find a byte  some-
   where to patch preventing this if successful operation is expected.

   Technical details:

   The  resident  portion of CORK is written  as  'position  independent'
   code; it will run *anywhere* in memory (no page boundarys even requir-
   ed).  When initiated, the CORK loader section moves the resident  part
   to a position 1/2k below BDOS, reducing your TPA by that small amount.
   It  then  patches several vectors (details below).   Control  is  then
   transferred to the high memory code, which then searches for a  speci-
   fied file (eg ZMP.COM). The current drive/user is searched first; then
   a  user defined alternate drive and user.  When the target program  is
   found, it is loaded at 100H and control is transferred to it, where it
   runs  normally  - 'unaware' that CORK is intercepting  and  converting
   console  characters on their way out.  CORK also  intercepts  whatever
   method  the program chooses to exit with; when this occurs,  CORK  re-
   stores all vectors to their original values ('releasing' memory in the
   process) and then actually does exit back to the operating system.

   CORK patches the BDOS jump vector at 0005, both to enable it to inter-
   cept BDOS console output calls and to properly reflect the reduced TPA
   size.   The program will intercept both BDOS calls 2 (Console  Output)
   and  6  (Direct Console I/O).  It will also intercept  console  output
   made  via  the BIOS jump table.  For exit purposes, the  program  will
   intercept a plain RET, a jump to zero or BIOS+3, or a BDOS call 0,  in
   case anyone does that.

   One other thing: Immediately after it is initiated, CORK copies all of
   the low memory area containing the 'command tail' information  (FCB's,
   command  tail itself, etc.) to the page of memory just below where  it
   is about relocate itself.  Later, just before handing control over  to
   the  'target' program, this information is restored.  Thus the  target
   program will be supplied with any filenames or other information spec-
   ified  on  the command line when CORK was initiated, just  as  if  the
   program had been initiated normally.

   This LBR contains the CORK source and two assembled COM files,  subse-
   quently  renamed.  The COM files are identical except that  one  (RUN-
   ZMP)  was assembled from CORK.Z80 with "ZMP.COM" filled in as  the  as
   the target program, and the other (TIPE) was assembled with "TYPE.COM"
   as  the  target (both were assembled with "A0" as  the  alternate  DU,
   btw). Typing RUN-ZMP (perhaps rename it ZM or something) will bring up
   the  ZMP  modem program ('available separately' -:) but  allow  easier
   communication with DOS boards.  The other program is really more of  a
   demo,  but could actually be used in to type files with DOS  character
   graphics (a small section of one such file I ran across is  included).
   The  TYPE.COM  included is simply C. Falconer's LT28,  though  a  line
   which strips the high bit was removed before assembly.  TIPE will call
   TYPE, and makes use of the command tail transfer described above.  Try
   "TYPE DEMO.TXT" and then "TIPE DEMO.TXT" and notice the difference.

   Disclaimer:  This program was written partly as a solution for  myself
   to a specific problem and partly just as a seed for the idea of remap-
   ping  graphics characters.  While I have every reason to  believe  the
   program  should run on any standard CP/M system and it has been  tried
   by  a  number of people, keep in mind that it is  'messing  with  your
   system' a bit so, as they say, "Standard disclaimers apply"...

   If it doesn't work, figure out why and let me know....

   NOTE: The program will not even *come close* to running without a Z80;
   for  one thing it is inherently based on relative jumps.  The  program
   *will*  check the Z80 condition, and abort gracefully with no  message
   if  running on an 8080/8085. (In fact, it will abort quietly  with  no
   message if almost anything else is wrong also, but there isn't much to
   go wrong.  Most likely it can't find the target program to run).

   Assembly: If you want to change the alternate DU's or the name of  the
   target program to be loaded or the character remapping table, you will
   need  to reassemble the source code provided.  Also note  an  assembly
   option that should be set to TRUE if your terminal will display the 7F
   character  ('rubout') as a solid grey or white box.  This will  result
   in  improved performance, and is *not* assumed in the COM  files  con-
   tained here.  First edit any changes desired into CORK.Z80; it's pret-
   ty self explanatory.  Then assemble.  The nature of the position inde-
   pendent  code  makes this a snap; no PRL's,  ZRL's,  RSX's,  GENSYS's,
   weird linker commands, debuggers, special programs, etc.  With SLR:

   Z80ASM CORK

   That's it; wait 2 seconds for the resulting COM file.  For M80:

   M80 =CORK.Z80

   and then, with either L80 or LINK

   L80 CORK/N,CORK/E    or:
   LINK CORK

   You may want to rename the resulting CORK.COM to something convenient.

   Obvious  enhancement:  While "+", "-", and "|" do an adequate job,  my
   console, like many others, does have some character graphic  capabili-
   ties.   The program as it stands now cannot make use of these  because
   of it's limitation of one-to-one character mapping (I was also  inter-
   ested  in  keeping the initial version generic).  For  a  system  that
   requires a 'go into graphics mode' escape sequence, the program  could
   be modified to put out that sequence when necessary.  A flag  internal
   to  the  remapping program could keep track of the current  mode,  and
   only  inject  the extra characters when necessary to switch  back  and
   forth.

   Obvious dumbness: Thanks to Ross Pressser who pointed out that my code
   was  organized in a dumb way.  While the program must relocate  itself
   to get "out of the way" before loading the target program, there is no
   reason for the 'target program loader' code to hang out after it's job
   is  done.   If it were at the bottom of the  relocated  section,  this
   would  be easy.  But alas, for the current version anyway, I added  up
   the  bytes and could not quite save a full page (ie make the  resident
   portion  1/4k) and I did not want to change the BDOS jump by some  odd
   amount  and I really hope no one needs TPA *that* badly and  mostly  I
   was  too lazy to rearrange the code at this point... But  if  enhance-
   ments  get made by myself or anyone else, that's where the extra  room
   can come from.

                                                - Steven Greenberg
                                                  14 December 1988