     18.  CHANGES

     Be sure to save your serial number/password (SNP) card and the putsnp
     program you received from Omen to use with future versions of DSZ you
     may download!

     The current DSZ version is maintained on GEnie (IBM Roundtable), EXEC-
     BBS, CompuServe (IBMCOM and CONSULT SIGs) as well as TeleGodzilla.

     DSZ is a popular program which has been the object of virus attacks.
     Pirated/hacked versions of DSZ have cost users and DSZ's developer
     thousands of dollars in lost time and other expenses, in addition to
     injuring of Omen Technology's reputation.

     Virus and Trojan code hidden in hacked/pirated copies of DSZ and
     programs claiming to "register DSZ" have caused loss of data.

     Name             Length                           Date        Time   CRC

     dsz.com          51628  Crunched   14%     44432  26 Jun 90   1:26p  e884
     dsz.exe          62001  Crunched   19%     50759  26 Jun 90   1:22p  b308
     PKZIP -vt 32 bit CRC: C06F1F5B   51628  dsz.com
     PKZIP -vt 32 bit CRC: 5A198AC3   62001  dsz.exe

     Your copy of DSZ should show this information as provided by

            arc v dsz
     or
           pkxarc -v dsz
           lharc v dsz

     ARC, and LHARC use a 16 bit CRC.


     ZIP uses a 32 bit CRC compatible with  the  Professional-YAM  and  ZCOMM
     "crc" command.
           pkzip -vt dsz
     The following Pro-YAM/ZCOMM command gives the 32 bit CRC for DSZ.COM:

     EXAMPLE: >>>c: crc dsz.com


     If your copy shows a different CRC or file length, insist on a
     legitimate copy and report the source of the bogus/pirated copy to Omen
     Technology Inc.  Omen Technology has received reports of serious
     problems caused by unauthorized patches to DSZ, and cannot assume
     liability for the performance of the resultant code.

     COM7 and COM8 are changed; see the "port" command above.

     A problem in the 1/17/89 and 2/2/89 versions corrupts files under





     Chapter 18 Pg 50      DSZ Reference Rev Jun-26-90        Typeset 6-26-90


     unusual circumstances.  Please delete all instances of the 1/17/89 and
     2-02-89 version.

     A reminder: the -Z option is effective only when it is given to the
     sending program unless both are Omen Technology products revised Jan 22
     1990 or later.

     If you use PREFIX= or ONAME= with the "sb" or "sz" commands, these
     pathnames must be entered in lower case unless the underlying file
     system supports upper AND lower case.

     A boundary condition bug in the implementation of the rz/sz -rr option
     has been corrected.  When using the -rr option, both sending and
     receiving programs should be a March 8 1990 or later version.
     Otherwise, files may be needlessly retransmitted.  This problem does not
     affect the -r option.

     June 25 1990: When a ZMODEM block length is forced, the receiving DSZ
     writes the data to disk before acknowledging the block.  With DSZ.EXE
     and its maximum 16384 buffer size, you may be able to avoid overrun
     (Line Status Register 02) problems receiving to slow disk drives by
     using:
     dsz pB16384 z pl16384 rz

     ZMODEM-90(TM) speeds up GEnie ZMODEM downloads; see DSZOPTS in Chapter
     6.

     The "sz" command had an undocumented fallback to YMODEM, this has been
     removed for reliability reasons.

     The SlugBait (-s) option now causes DSZ to return success (0 exit code)
     if at least one file is transferred.

     April 11 1990: Enhancements for more efficient multitasking under
     DESQview and DESQview 386.  Code which prevented IRQ conflicts between
     COM1/COM3 and COM2/COM4 has been removed to allow use of COM7 and COM8
     without interference from DSZ running on COM1 or COM2..

     ZIP replaces ARC as the standard download distribution format on new
     files.

     March 21 1990: DSZ now sends the CANCEL sequence if it runs out of disk
     space while receiving a file with ZMODEM.

     DSZ now defaults to "handshake both" if the clear to send signal is high
     when DSZ selects the comm port regardless of the initial "baud rate".

     The P parameter can be set to -1 to disable the FIFO on the Western
     Digital WD16550 chip.  The WD16550 FIFO has been observed to lose
     characters when transmitting at slow baud rates.  A more elegant
     software solution to this hardware problem may be discovered in the





     Chapter 18 Pg 51      DSZ Reference Rev Jun-26-90        Typeset 6-26-90


     future.

     Feb 25 1990: Doco change only. The "R" numeric parameter or the
     "restrict" command may be used to force partially received files to be
     deleted.  These features have been in DSZ for a long time, but never got
     into DSZ.DOC.

     Feb 18 1990: DSZPORT now accepts "portx" style arguments in addition to
     the traditional decimal number.  The -Wn option has been improved.

     Jan-28-1990: Doco improvements, especially to the "In Case of
     Difficulty" chapter.  BBS registration clarified for those that bother
     to read it.  Qmodem batch files fixed.  No change to the DSZ software.

     Jan-22-1990: ZMODEM-90(TM) extensions:

     Receiver specified window size: The -Wn option operates similarly to the
     -wn option.  The -Wn option is specified to the receiver, which sends
     this information to the sender.  Pro-YAM, ZCOMM and DSZ versions
     beginning with Jan 22 support this.

     Specified extra escaped characters: The "zmtxesc" and "zmrxesc" allow
     extra characters to be escaped when sending (zmtxesc) or receiving
     (zmrxesc).  Zmtxesc is effective sending to any ZMODEM program.  The sz
     commands in Omen products after Jan 22 1990 except for DSZ.COM recognize
     incoming "zmrxesc" requests.  TThe zmrxesc and zmtxesc string parameters
     consist of one or more printing characters corresponding to the control
     characters to be escaped.  To escape NULL:  set zmrxesc "@"

     Since DSZ does not support string parameters, a -Q<string> option unique
     to DSZ performs the same function as zmrxesc and zmtxesc.  If the
     Q<string> option is used in DSZOPT, it must be last.  To escape NULL:
     dsz sz -Q@ file.ext

     MobyTurbo(TM):

     MobyTurbo optimizes throughput on ZIP, ARC, and similar files without
     sacrificing ZMODEM's famous reliability on noisy lines.  MobyTurbo works
     with standard modems, error correcting modems with hardware flow
     control, and over paths that support ZMODEM and do not "eat" or
     otherwise respond to control characters.  This includes all paths that
     support YMODEM-g (or would except for errors).

     Activate MobyTurbo with the -m option to one or more of: sz command, rz
     command, or DSZOPT environment variable.

     ZMODEM over 7 bit paths:  (Not supported in DSZ.COM)

     A pair of ZMODEM-90 programs with 7-bit support operating over a 7 bit
     path should detect that fact and switch to one of two 7-bit path
     compatible encodings.  For testing, this can be forced with a "-E"





     Chapter 18 Pg 52      DSZ Reference Rev Jun-26-90        Typeset 6-26-90


     option.

     Default 7-bit mode is RLE compression and 8th bit quoting similar to
     Kermit but more efficient because not so many control characters are
     quoted.  Use this default for text files.  Rubout and all control
     characters can be escaped with the -e option.  Individual control
     characters can be escaped with "zmtxesc" and "zmrxesc".

     Pack-7 instead of quoting is activated with the -P option.  (-P has no
     effect on 8 bit paths.) Pack-7 packs 4 bytes into 5 printing characters.
     This is more efficient than quoting for files where 25% more 8th bits
     appear than the number of characters saved by RLE compression.  (This
     statement applies to GIF, ARC, ZOO, and ZIP files.  It may or may not
     apply to other binary file formats, depending on the data.) Pack-7 will
     match or beat standard Kermit on ZIP files, even when Kermit has use of
     all 8 bits.

     SUPK412.ZIP 75136 bytes sent at 2400 bps direct connect from an
     Everec 1800 AT clone 8mHz/0ws to an 18 mHz Intel 386 motherboard.

     8-Bit line
     cps     Protocol/command
     156     MS Kermit 3.00 to MS Kermit 3.00  (defaults)
     182     MS Kermit 3.00 to MS Kermit 3.00  (windows=2 length=2000)
     184     MS Kermit 3.00 to Pro-YAM 17.51 (windows=2 length=2000)
     231     Pro-YAM 17.51 ZMODEM (defaults)
     237     Pro-YAM 17.51 ZMODEM-90(TM) MobyTurbo(TM) (sz -m)

     7-Bit line
     cps     Protocol/command
     156     MS Kermit 3.00 to MS Kermit 3.00  (windows=4 length=2000)
     190     Pro-YAM 17.51 ZMODEM-90 PACK-7 (sz -EP)

     Kermit transfers used 8 bit CRC, ZMODEM used 32 bit CRC.


     ************************************************************************
     ************************************************************************

     WHAT TO LOOK FOR:

     Performance     difference     with     MobyTurbo,     possible     side
     effects/incompatibilities.   MobyTurbo  logic  tests  for  software flow
     control incompatibilities: when does this test fail?

     Automatic detection of 7-bit paths.  Spurious detection of  7-bit  paths
     and failure to detect 7-bit paths.  (DSZ.EXE only)


     12-13-89  The Virus check was removed because of user confusion and slow
     startup under certain conditions.  Code has been added to prevent and/or





     Chapter 18 Pg 53      DSZ Reference Rev Jun-26-90        Typeset 6-26-90


     recover from "line status register 18" errors.

     10-28-89 A T may be appended to DSZOPT or "dsz t  -T"  may  be  used  to
     force  DSZ  to  exit  after  it has recognized a ZMODEM AutoDownload(TM)
     request.

     10-24-89  BBS registered copies (serial  numbers  8000-8999  and  20000-
     23999) are now fully featured.

     The BBS registration form has been  modified.   Please  read  this  form
     carefully  before  applying  a  BBS  serial  number.   Use of BBS serial
     numbers (4000, 20000 series) acknowledges acceptance of this contract.

     The IMP/KMD compatibility file length information in the  YMODEM  header
     generated by the sb command now uses the correct byte ordering.  Changes
     to the XMODEM/YMODEM sz/sb commands were made  to  accommodate  programs
     that ise CK or CKL.  (As predicted in 1985, networks sometimes interfere
     with these sequences.)

     Files passed over because of creation errors at the  receiving  end  are
     now  counted  by the "sz" command as errors.  The receiving program must
     be a 9/89 or later version for this to be effective.

     The specified directory form of the rz and rb commands has been  enanced
     to accommodate certain forms of erroneous syntax.

     6-19-89 A documentation error (concerning DSZPORT) was corrected in  the
     DOC file.

     5-25-89  Corrects a protocol negotiation problem encountered when the rz
     or sz -e option is used.

     Host programs can now specify an alternate CANCEL sequence (not used for
     DOS and Unix).

     The ZMODEM "Slow Send" mode inserts a brief pause after  each  subpacket
     when  invoked with the -F option, or automatically when the "sz" command
     detects failing flow control.  The zmodem F numeric  parameter  (default
     1) sets the pause in tenths of seconds.

     4-24-89 The -rr option has been improved.  Long file compares  are  done
     in  two  stages  to  save  time  when  the  first portions do not match.
     Diagnostic code and undocumented commands have been removed to  decrease
     the program size.

     The 4-18 version introduces ZMODEM variable length headers of up  to  16
     bytes  information  field instead of the previous fixed 4.  Selection of
     variable length header capability is automatic and downward  compatible.
     Variable   length   headers   allow   future   extensions   to  ZMODEM's
     capabilities.






     Chapter 18 Pg 54      DSZ Reference Rev Jun-26-90        Typeset 6-26-90


     ZMODEM Crash Recovery now understands the  -rr  option  to  compare  the
     CRC-32   of  the  assumed  common  file  segment  before  continuing  an
     incomplete file transfer.  The "zmodem R" numeric parameter may  be  set
     to limit the number of bytes in the files that are compared; the default
     R value of 0 allows all of the file to be compared, an  R  value  up  to
     32000  (up  to 2 billion on 32 bit flavors) limits the comparison to the
     first R bytes of the two files.  The ZMODEM -rr option is  supported  by
     Omen Tech versions April 18 1989 and later.

     When ZMODEM Crash Recovery detects incompatible source  and  destination
     file  contents,  the  destination  file  is now truncated to zero length
     before proceeding  with  the  transfer.   Crash  Recovery  requires  the
     destination file to be no longer than the source file.

     Error reporting on unregistered copies has been enhanced  to  point  the
     user to solutions described in the relevant chapters in DSZ.DOC.

     3-18-89 In order to work around a bug in the  new  TCOMM  bbs,  DSZ  now
     defaults  to  "handshake  on"  if the speed is greater than 2400 and the
     clear to send signal is high when DSZ selects the comm port.

     The "o" command has been added to disconnect the modem after a  terminal
     session:  "dsz  t  o" disconnects the modem when the terminal session is
     completed.

     The "P" (capital P) numeric parameter (q.v.) has been added  to  display
     and control the UART fifo on some clone chips.

     BBS registrations postmarked after Feb 28 1989 must be accompanied by  a
     paid  DSZ  registration.  The free program expired Feb 28 1989.  Outside
     help has been hired to process and verify  applications  received  under
     that program.

     2-23-89 The term function now sends BREAK in response to the ALT-B  key.
     Handling  of  the  Ctrl-Break  vector  has  been  changed so an untimely
     keyboarded Ctrl-C or Ctrl-Break will not hang DOS.

     2-15-89  DIRRX is enabled for BBS registrations (8xxx  numbers).   Logic
     has  been  added  to  simulate  transmit  interrupts  on chips that have
     problems in this area.  The "A" command does not  require  registration.
     An  interaction between ONAME= or PREFIX= and the file count display has
     been removed.  Time/date conversion routines have been enhanced to  deal
     with  files with missing dates.  The "v" command has been added to allow
     bbs programs to interrogate DSZ's serial number.

     2-06-89 A spurious error message at the completion of  YMODEM  downloads
     with  a  download  directory  specified  on  the  command  line has been
     eliminated.

     2-05-89 DSZ now returns a non 0 status unless at least one file has been
     transferred.    An   inappropriate   pathname/disk  specifier  check  on





     Chapter 18 Pg 55      DSZ Reference Rev Jun-26-90        Typeset 6-26-90


     specified download directories has been removed.

     Previous versions:

     Added the "A" command to prevent pcAnywhere host mode  from  locking  up
     DSZ.   SlugBait  logic  has  been  simplified, reporting any failed file
     transfer where any of the last 1K of the file was sent with Q status.

     Introduced ZMODEM RLE compression with the -Z option.   (registered  DSZ
     copies  also  accept "Z" in the DSZOPT environment variable.) ZMODEM RLE
     compression packs runs of the same character in two or  three  character
     sequences.    Compression  is  useful  for  screen  dumps,  uncompressed
     workspaces, compiler listings, and other  files  rich  with  strings  of
     repeated  characters,  but  not  .ARC,  .ZOO and other compressed files.
     Compression percentages range from -1 per cent  for  already  compressed
     files  to  more  than  1000  per  cent  (10x  speedup!) for the Personal
     Computing text file benchmark(!).  When sending to programs that do  not
     support  ZMODEM compression, the -Z option is ignored.  The -Z option is
     effective when specified to the sending program only.

     Good news for tired frog stompers!  The ZMODEM rz/sz  programs  are  now
     available  in a VMS C flavor.  The VAX/VMS source files are contained in
     the RZSZ.ARC (RZSZ.ZOO) archive file.

     "Handshake slow" has been added to disable the RTS signal to  the  modem
     while writing to disk, even if the interrupt buffer is not chock full of
     bytes.  This should help systems with  excessive  interrupt  latency  on
     disk writes.

     Setting the v (verbose) parameter to  1  or  greater  causes  serialized
     copies to ring the bell when a transfer is done.

     DSZ.DOC has been extensively rewritten and  reorganized.   DSZ  supports
     the  advanced  buffering of the National NS16550AN, NS16550AFN and Intel
     82510 serial interface devices.   Please  refer  to  the  subchapter  on
     "Brain Damaged UARTs".
