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April 18, 1987
This is the READ-ME file from the Z80DIS.LBR package, version 2.2
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A personal note from the programmer:
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I wrote this disassembler because I could not find another
that would really open up a large foreign program for inspection.
RESOURCE and all of its spin-offs give you only a pin-hole look
at a program without indicating the important interactions with
other parts of the code. Without the interactions and a wider
view, figuring out the code purpose or data type of a code block
is very hard.
Z80DIS eliminates the narrow pin-hole view of a program
provided by an interactive display. Z80DIS provides fully
automated analysis of the code structure, well formatted output
in both assembler and printer formats, a complete cross-reference
coded by reference type, and commenting of DOS interactions.
Recent improvements in this latest version add further utility
and increase the ability to handle even larger code segments.
For those who prefer an interactive approach to disassembly,
I recommend the combination of Z80DIS with the interactive
disassembler DAZZLESTAR (DZ) by John Washington in England. Use
Z80DIS for the automated analysis of the underlying structure and
use DZ for the interactive refinement of the code. John has
provided a DZ command (namely KG) to read the break table
produced by Z80DIS.
As CP/M users are getting less and less support for problems
with existing 8080 or Z80 software products, maintenance of that
software has fallen to the CP/M users themselves. Z80DIS lets you
examine the software and repair the problem yourself. I hope that
you will find Z80DIS as useful as I have.
Kenneth Gielow
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Z80DIS 2.2 04/18/87
Version 2.2 change note:
Version 2.0 added artificial intelligence to Z80DIS.
Version 2.1 corrected a small bug in the processing of INC,
DEC, and LD using index registers IX and IY and enhanced the
distinction between ASCII blank (20 hex) and the instruction
"JR NZ,xxxx" (also 20 hex).
Version 2.2 modifies the output format for M-80 assembler
compatibility. Increases the size of program that can be
disassembled by moving cross-reference tables to virtual
memory on disk. Fixed several minor bugs. Interprets CP/M
DOS calls and comments such calls by the function performed.
Caveat: If you are running a system with single sided disks, you
probably do not want to upgrade from version 2.1 to version
2.2 because of the increased off-loading of memory functions
onto disk files
Z80DIS is a disassembler for Z80 based CP/M systems. Z80DIS is
designed to generate Z80 mnemonics and prepare an assembly
language file with many special features for ease of
understanding the intent of the disassembled code. The source for
Z80DIS has grown to 8400 lines of pascal code.
With Z80DIS versions 2.0 and higher, you need know very little
about the format of the *.COM file to produce a nearly finished
source file in most cases. In addition a large number of
convenience features and defaults have been added that were not
present in version 1. The Z80DIS change history for version 2.x
follows at the end of this paper.
Both the Z80DIS program and the Z80DIS documentation are (C)
Copyright 1985, 1986 and 1987 by Kenneth Gielow; All Rights
Reserved. While I am freely distributing the binary code for non-
profit use, I am reserving the source code as a trade secret.
This program requires a Z80 based computer running CP/M version
2.2 or higher. The code was compiled for a 50K TPA; the top
address is C7FF. This slightly small size was done for
compatibility with CP/M 3.0 and ZCPR3.
The following files will be found on Z80DIS21.LBR for this
program distribution library package:
Z80DIS.COM - the disassembler program
Z80DIS.000 - overlay file for Z80DIS
Z80DIS.001 - overlay file for Z80DIS
Z80DIS.002 - overlay file for Z80DIS
ZDINSTAL.COM - a terminal command installation program
ZDINSTAL.MSG - contains text of ZDINSTAL messages
ZDINSTAL.DTA - contains terminal characteristics data
Z80DIS22.DQC - an installation manual. (Squeezed format)
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Z80DIS 2.2 04/18/87
The three ZDINSTAL files are based on the TURBO Toolbox GINST
program and will tailor the display command sequences for your
terminal. The DOC file is the text of a short user manual which
explains use and installation of the program.
The interactive displays for parameter specification make the
program easy to use. All control parameters have defaults preset
to the most likely values.
FEATURES OF Z80DIS
------------------
The major feature of Z80DIS is an extensive analysis of the
memory usage by the program under investigation. This analysis
capability forms the basis for an automatic partitioning of the
code to generate the break table. This analysis also produces a
fully-annotated cross reference of all addresses.
A disassembler must know whether the bytes are instructions or
data in order to proceed. Z80DIS is the first disassembler to
produce its own break table for this purpose. Some previous
programs, such as RESOURCE, have included a search for ASCII text
regions, but have left the verification and interpretation up to
the user. Most other disassemblers are fooled by the trick of
adding nonsense bytes after jumps to cause the analysis to fall
out of synchronization with instruction code interpretation.
Z80DIS produces an output listing which itemizes all addresses
referenced by the code, distinguishes types of label references,
marks subroutines and jumps and produces an annotated cross-
reference. This listing shows the exact mode of usage for every
reference: Jump absolute, Jump relative, Call, Restart, Load 16-
bit, Store 16-bit, Immediate 16-bit, Load 8-bit, Store 8-bit. In
version 2.1, this listing also shows the break table region of
residency for each label so that you may inspect the list for
inconsistencies.
An address labeling convention assists in understanding the
assembly code generated. Each label generated on the assembly
listing indicates, by format, not only the generic type (Jump,
Call, Data, Other) of any references, but also the singularity of
the reference. For example, J$02E3 used at address 02E3 indicates
that only one reference was made to address 02E3 and that that
reference was a JUMP.
In addition to helping you by automatic analysis of memory use,
Z80DIS also assists you by styling the presentation of the disas-
sembled code. The disassembled code is output in two forms: Both
the usual *.MAC file and a printer formatted *.PRN file.
The *.PRN file is styled to look like the output of an assembler
with both the instructions and assembled bytes shown. The juxta-
position of the hexadecimal bytes and the assembly mnemonics
allows the user to recognize errors caused by an incorrectly
defined break table.
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Z80DIS 2.2 04/18/87
DOCUMENTATION NOTICE
--------------------
The original, version 1, user manual ran forty-plus pages and
gave extensive examples and used disassembly of the public domain
program D.COM as an example.
The version 2 manual is now eighty eight pages of detailed, what-
if instructions and a dissertation on understanding and handling
large or complex code modules.
As the binary code for Z80DIS is now running 108K bytes and the
ascii text for the manual is over 200K bytes, there is no way
that I can get system operators to carry both. I feel that the
program is largely self explanatory so that you can get started
very well with only the minimal help of the included DOC file.
The short user manual included here deals only with installing
the Z80DIS program and doing a simple disassembly. For more
serious work you will want the full manual.
The longer manual expands on the discussion of the features and
explains the step-wise approach to dealing with much larger
source codes. The manual also deals with disassembling code which
relocates itself. Extensive examples are included. All error
messages and secondary options are discussed in detail.
The full Z80DIS USER MANUAL is available by mail. I am asking a
nominal charge of $20.00 which includes the printed and bound
manual, postage, handling, and an update notification service.
You are granted the right to make not-for-profit copies of the
manual. The program itself is not available by mail as I do not
have extensive, multi-format disk copy capability. The
notification service will consist of a letter to you anytime a
new version is released so that you may be on the lookout for it.
To order a copy of the Z80DIS USER MANUAL, send a request with
your name, address, and a check for $ 20.00 to --
Kenneth Gielow
79 Tulip Lane
Palo Alto, CA 94303
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