dales@pro-novapple.cts.com (Dale Smith) (02/18/91)
The following is the substance of an announcement posted on AOL, GEnie, CIS
from Andy Nicholas concerning Zmodem drivers for a number of Apple II
Bulletin Board System programs.
=========================== Begin Announcement =============================
Zmodem comes to GBBS!
--------------------
This past summer, between writing different versions of Shrinkit and
GS-ShrinkIt, Andy Nicholas took time out to write Zmodem drivers for several
different bulletin board systems. If you are the sysop of a bulletin board
which uses GBBS's ACOS language you may want to take advantage of a very good
development.
You may order a copy of the Zmodem drivers which work with GBBS directly from
Andy. More details about this later.
But before more those details, here's a summary of some of the features of
the Zmodem drivers which Andy is making available.
Features:
--------
o Both RZ and SZ completely conform to the public domain Zmodem 2.0
implementation by Chuck Forsberg using 16-bit CRCs.
Both Zmodem Send (SZ) and Zmodem Receive (RZ) are completely and
correctly implemented and take approximately 4k of space in the
GBBS "use" buffer along with an extra 8k of buffer space in
auxiliary memory.
o There are special versions of RZ and SZ which use the Apple IIc's
vertical-blanking interrupts for timing considerations.
o Speed. Zmodem is a streaming protocol. This allows for faster
transfers than Ymodem and helps 9600 baud transfers go close to
their theoretical maximum.
o Better error recovery. Zmodem can recover from errors better than
Xmodem or Ymodem. If you have a really noisy line, chances are
that Zmodem will continue the transfer long after Xmodem and Ymodem
have given up.
o Network friendly. RZ and SZ will not "jam" a network by sending
XOFF characters in its data stream. Instead these characters are
sent using Zmodem's escaping mechanism. What this means is that
you won't have to setup your local node of PcPursuit or other
service when calling a BBS that uses RZ and SZ. No special
parameters for your node should be needed. Just call and transfer.
o Zmodem is a "batch" protocol. Both drivers support sending and
receiving batches of files.
o Auto-Download support. If your terminal program supports
Auto-Download, then using RZ with your BBS will automatically tell
your communications software to begin downloading without ever
touching a key!
o Download resumption. If you have a communications program which
supports resuming a download after you have been disconnected while
downloading a huge file... no problem. Just call back and begin
the download at the point where you left off. These Zmodem drivers
properly support doing just that.
o SZ (the BBS end receiving a file via Zmodem) supports both upload
resumption (if you, as a sysop, like incomplete pieces of files
laying around on your BBS), renaming an existing file, or just
deleting a file on the BBS which the user is trying to upload. So,
in the case of a duplicate file, you have great flexibility in what
to do.
o Automatic block resizing! Xmodem sends files with 128 byte blocks.
Ymodem sends files with both 128 byte and 1k blocks. Zmodem can
use any block size up to 1k. When downloading, RZ will take note
of how noisy the phone line is and if there are enough errors RZ
will halve the block size until some data gets through.
If you have clean phone lines then RZ will start increasing the
block size until it is streaming 1k blocks. So, the cleaner your
phone lines are: the faster your transfers will be.
If during the course of a download the phone lines become very
noisy then RZ will make the blocks smaller -- and if the line
becomes less noisy later during the download, RZ will start sending
larger blocks.
* Just a note. At this time, although plenty of Macintosh and IBM PC
communications programs like ZTerm and ZComm support Auto-Download and
file resumption, no current Apple II communications software is known
which does. ProTerm 2.2 and prior do not support Auto-Download or
file resumption, although it is conceivable that ProTerm 3.0 will
(we can hope).
What you need to use RZ and SZ:
------------------------------
An enhanced (65c02) 128k Apple IIe, IIc, or Apple IIGS
GBBS "Pro" 1.3 or later (preferably later)
A good working knowledge of GBBS's language, ACOS.
How much will the drivers cost:
------------------------------
Andy is asking $21 for the GBBS Zmodem drivers.
What your $21 will get you:
--------------------------
SZ and SZC (Send Zmodem and Send Zmodem for the Apple IIc)
RZ and RZC (Receive Zmodem and Receive Zmodem for the Apple IIc)
Notes on how to write a simple module for your BBS to support Zmodem
transfers.
The latest versions of ShrinkIt, GS-ShrinkIt, II+ ShrinkIt, and
AUTO-Unshrinkit will be included as a bonus (since they are, after
all, freely available).
Because Andy is keenly aware of the amount of piracy that a product like this
will undergo, he has attached the following stipulations:
o Please pay by check. Orders received in cash will be returned.
o He will wait up to 3 months until he has received 40 orders before
shipping anyone's order. This means that the sooner he receives 40
orders, the sooner everyone will receive their copy of Zmodem for
GBBS. If you are not prepared to wait a while -- because he can't
predict how long it will take to receive 40 orders -- then please
do not order this.
o If he does not receive 40 orders, he will return everyone's checks
uncashed.
o He is not going to attempt to hunt down those who choose to
illegally distribute what he's written -- he only hopes that some
of them have the decency to pay for what they use. There isn't
any tomfoolery in the drivers either. No secret codes or
encryption or serial numbers. If you buy a copy, he will send you
a copy. It's as simple as that.
If this sounds reasonable to you, then you may send your order with a check
for $21 to:
Andy Nicholas
1180 Reed Ave, Apt 12
Sunnyvale, CA 94086
and make sure you specify what kind of disk (3.5" or 5.25") on which you need
the Zmodem drivers - and where to send the Zmodem drivers.
About the Author:
----------------
Andy Nicholas is the author of the freeware programs ShrinkIt, GS-ShrinkIt,
ShrinkIt for the Apple II+, and AUTO-UnShrinkIt (shrinkit archive
scavenger/extractor) and is currently employed by Apple Computer to work on
the Apple IIGS Finder. This is work that he did before going to Apple and
work that he's continuing in his spare time. He is a believer in low-cost,
high-quality software. He also believes in trying to get that software to as
many people as possible.
At this time (1/27/91), there are also tentative plans for the distribution
of Zmodem drivers for both ProLine and the Prime BBS system. These Zmodem
drivers have already been written and tested, although he expects that he
will almost certainly not handle their distribution.
If you have questions about the Zmodem drivers, suggestions for future
versions of ShrinkIt, or suggestions for the Apple IIGS Finder, he invites
you to contact him on America-Online, GEnie, CompuServe, and the internet at:
America-Online & Genie: shrinkit
CompuServe: 70771,2615
Internet: shrinkit@apple.com
========================= End Announcement =================================
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