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[ THE KAY*FOG RBBS | Filename=CPM-CC27.ART | posted 07/05/86 | 200 lines 11k ]
The CP/M Connection Originally published in
by Computer Currents
Ted Silveira 5720 Hollis Street
(copyright and all rights reserved) Emeryville, CA 94608
May 20, 1986
Z: THE FINAL CHAPTER (FOR NOW)
Now that I've talked about the _what_ of the Z-system, let me say a
little about the _how_. Let's start with an overview of what happens
when you install ZCPR3 (or ZCPR3 plus ZRDOS) on your CP/M computer.
The typical CP/M computer has 64K of RAM (random access memory)--
that's actually 65,536 bytes (because 1K equals 1024 bytes). You can
imagine this 64K RAM as a single stack of 65,536 pigeonholes or
mailboxes, piled one on top of the other, each mailbox containing a
single byte of information.
Figure 1 shows how this RAM is allocated in a typical CP/M system.
At the very bottom of RAM (addresses 0-255) is a reserved block of 256
bytes used by CP/M. The rest of the CP/M operating system lives in the
uppermost section of RAM, taking up about 8-9K. The space between the
reserved block at the bottom and CP/M at the top is the _transient
program area_ (TPA), the space in which programs like WordStar,
SuperCalc, and dBase II run.
As you can see, the CP/M operating system itself is divided into
three parts. The CCP (console command processor) interprets commands
entered at the A> prompt and contains the built-in command such as ERA
and DIR. The BDOS (basic disk operating system) handles things like
writing and reading disks, creating and erasing files, and sending
characters to the screen. The BIOS (basic input/output system) works
intimately with the computer hardware, turning BDOS commands like "open
a file" into "move the disk drive head of drive A to track 1" and so
forth.
Figure 2 shows the same typical CP/M computer with the Z-System
installed. Three things have happened. First, ZCPR3 has replaced
CP/M's standard CCP. Second, ZRDOS may or may not have replaced CP/M's
standard BDOS (it's optional--see last issue's column for a brief
description of ZRDOS' advantages). Third, the entire operating system
has been moved lower in memory to make room for the ZCPR3 buffers and
command packages. Because the operating system has been lowered, the
TPA is now smaller by anywhere from 1K to 6K or more.
That's the overview. When it comes to installing the Z-System on
your computer, you have three routes you can take, four if you have a
Kaypro.
[Manual] The manual installation is the most difficult and yet the
most flexible method. (If what follows is too technical for you, just
skip it--there are easier methods.) Essentially, you start with the
full set of ZCPR3 source files and build a Z-System of exactly the size
and features you want. To do this, you need to know some assembly
language, have a macro assembler (like Digital Research's MAC or
Echelon's own ZAS), and know something about your computer's BIOS.
Briefly, these are the steps. Collect the ZCPR3 source files and
documentation. Then select the ZCPR3 features you want--you don't have
room for everything.
Next, figure out how much space you need for these features--how
much for the FCP, the RCP, and so on. You work by cut-and-fit--do a
trial assembly, check the size, juggle the numbers, do another trial
assembly. Once you have the size set, use the CP/M utility MOVCPM to
move the operating system lower in RAM to make room at the top of memory
for ZCPR3's buffers and command packages. Then add a short routine to
your computer's BIOS to set all the ZCPR3 buffers to the proper values
on startup.
Finally, assemble your chosen ZCPR3 package into a HEX file and use
DDT to merge it with your new, smaller CP/M system, creating a new
system image that you'll use to SYSGEN all your disks.
[Semi-Automatic] Through bulletin boards and users groups, you can
find a number of ZCPR3 installation "kits" for various computers. These
kits are basically manual installations in which the hard work has
already been done by someone else.
What you get in one of these kits is a set of already assembled
ZCPR3 files. You must created a smaller CP/M system with MOVCPM and
then merge the kit files with it using DDT. None of the kits I've seen
requires that you know any assembly language, only that you know how to
use DDT, MOVCPM, and SYSGEN.
Obviously, this installation is easier than the manual one. The
drawback is that both the system size and the ZCPR3 features have
already been selected--you can't change them without getting the ZCPR3
source files and reassembling them. But if you find a kit that has the
features you want (and most do have a good selection), you're in
business.
[Automatic] Echelon, Inc., the distributor of ZCPR3, now offers
automatic installation packages starting at $49.95 (and going up,
depending on whether you want ZRDOS and whether you get the ZCPR3
utilities from Echelon or from public domain sources).
This automatic installation really is almost automatic. You copy
the master disks (consolidating files on one disk if you have room),
boot up the copy, and then run a SUBMIT file by typing [SUB ZCCOM] at
the A> prompt. As the SUBMIT file runs, it will create the various
files you need. At the end of its run, it will run a terminal select
program so that you can install ZCPR3 for your terminal type. Then the
SUBMIT file passes control to your new system.
This method gives you a slightly different kind of installation
from the manual and semi-automatic ones. You end up with a COM file
(Z.COM or Z3.COM) that contains your Z-System. You run this program
from the A> prompt, and it loads your Z-System. You can set your disks
to automatically run this COM file on any cold boot, so that you don't
have to bother with running it yourself. You can also exit this Z-
System at any time and return to normal (drab) CP/M by running a little
program called ZCX.COM.
There are two main drawbacks to this method of installation.
First, you have to pay for it (though the price is certainly
reasonable). And second, as in the semi-automatic installation, you
don't have any choice of features or system size--you take what you get.
The package has a good selection of features, and you can always
substitute a new RCP (resident command package) or FCP (flow command
package), but it's simply not as flexible as a manual installation.
[Bootable Disks] Kaypro owners have yet one more choice, the
easiest installation of all. Echelon now sells a "bootable" Z-System
disk (including ZRDOS) for most Kaypros, including those with the Advent
TurboROM and all stock Kaypros except those with the U ROM (CP/M 2.2u).
To make this installation, you just put the Echelon disk in the A
drive and hit the reset button. The computer will boot up the Z-System
and run an installation program that gives you a choice of installing
one of three versions of the Z-System. Choose one, put a blank disk in
your B drive, and relax. The rest of the installation proceeds
automatically. And unlike the automatic installation method I mentioned
above, this method gives you a Z-System that boots up like any normal
disk--no extra COM file to run. (Also, this package comes with a manual
that's better for beginners than the usual Z-System documentation.)
The drawbacks are the same as those of the previous method. You
have to pay for it, and you have less flexibility than with a manual
installation (though you do get to choose from three different-sized
systems).
[Final Words] The Z-System as a whole does have some possible
drawbacks. First, because the Z-System takes more room than standard
CP/M, there's always a chance you may encounter a conflict with some
other program (i.e., one that wants more memory than is available with
the Z-system installed), especially if you're also running a memory-
resident program like SmartKey or Write-Hand-Man. Almost all the major
commercial and public domain programs I know of work fine, including
WordStar and dBase II.
Second, it takes some time to learn your way around a full Z-System
with menus, aliases, and all the trimmings. But you don't need to use
all the Z-System's power right away, and learning Z is considerably less
difficult than learning to use WordStar, for example. Third, the Z-
System documentation isn't as good as it could be. It's full of
detailed information, presented in an orderly and consistent way, but
it's too dense to be readily accessible to beginners. Partly in
response to this problem, Echelon maintains a list of "good neighbor
helpers" (people willing to give advice on various systems) and puts out
the _Z-News_, a biweekly newsletter. There's also a very large network
of Z-Nodes, bulletin boards dedicated to exchanging information about
the Z-System.
Overall, ZCPR3 and the Z-System are tremendous improvement over
standard CP/M. As I've said before, the Z-System is a computer
supercharger--it makes many things easier and makes other things
possible that weren't possible before. Once you try it, you won't go
back.
Information on ZCPR3 and accompanying programs:
Echelon, Inc. Main Echelon/ZCPR3 bulletin board:
855 N. San Antonio Road Z-Node Central - 415/489-9005
Los Altos, CA 94022
415/948-3820
FIGURE 1 (Typical CP/M RAM) FIGURE 2 (Typical ZRDOS RAM)
(approximate only) (approximate only)
------------ -CP/M OPERATING SYSTEM- ------------
| BIOS | basic input/output system | buffers | space for ZCPR3 buffers,
|----------| | | RCPs, FCPs, etc.
| BDOS | basic disk operating sys |----------|
|----------| | BIOS | basic input/output system
| CCP | console command processor |----------|
|----------| |BDOS/ZRDOS| standard BDOS or ZRDOS
| | |----------| replacement
| | | ZCPR3 | ZCPR3 replacement for
| | |----------| standard CCP
| | | |
| | | |
| | | |
| | | |
| TPA | transient program area | TPA | transient program area
| | (usually 55-56K) | | (typically 50-54K)
| | | |
| | | |
| | | |
| | | |
|----------| |----------|
| reserved | | reserved |
------------ ------------
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Ted Silveira is a freelance writer and contributing editor to several
computer-oriented publications. He appreciates suggestions or feedback
and can be reached through the KAY*FOG RBBS (415)285-2687 and CompuServe
(72135,1447) or by mail to 2756 Mattison Lane, Santa Cruz, CA 95065.
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