Take the hard work out of disassembly by writing direct to
disk
The normal run of the mill disassemblers available
will produce a listing to printer or screen. This is normally very
fine and informative but sometimes we need to customise an existing
object code program and to do this the whole disassembly has to be
typed in by hand, modified and reassembled. SOURCE WRITER makes this
task redundant as you can disassemble your choice of object code and
obtain a disassembled source file on disk ready to modify and
assemble as you please.
SOURCE WRITER will disassemble a disk file or a
collection of disk sectors, a cassette file or an area of memory.
Try 0600 to 0620 from memory, for example, and you'll get a
disassembly of the cassette loading routine. The format of the
disassembly is: line no., address, instruction, and optional data
such as Hex and ASCII representation of the code to assist in
determining text. An example output is - 11 A0600 PLA *68 " followed
by ASCII representation.
The address noted in the label field is essential
for tracing branch JMP and JSR instructions. These can be deleted
and replaced by your own labels or left as they are, as you wish.
The source files can now be customised and assembled as required.
SYNASSEMBLER OR ASSEMBLER EDITOR?
The files generated by SOURCE WRITER are
Synassembler compatible but this can easily be made Assembler Editor
compatible by making the following changes:
Replace '
.OR$' in line 430 with'* = $'
Replace '
.HS ' in line 480 with '.BYTE $'.
Replace '
*' in line 880 with ';'.
USING THE PROGRAM
After initialising, SOURCE WRITER will display the
options available
1 Object
code from disk
2 Object code from cassette
3 Object
code from memory
4 Object code from disk by sector
Option 1 will read a DOS object code file into F$
for disassembly. Option 2 will read a cassette based object code
file into F$. Option 3 will transfer a specified area of memory (ROM
or RAM) into F$. The start and end addresses are required in
hexadecimal. Option 4 will read a sequence of sectors into F$ in two
ways. The first prompt is for starting sector, the second prompt
asks if you are anticipating a six byte header. With a DOS disk in
drive 1 SOURCE WRITER will disassemble the first 3 boot sectors,
however, if you are not expecting a six byte header SOURCE WRITER
will next ask for the origin the disassembly is to start at
(hexadecimal of course) and the final prompt will then ask for the
final sector to be read.
After one of the four options has been completed
the next prompt is "Disassembly with Hex Y/N" a 'Y' will cause a
note of the object code to be made in the remark field in the line
of a disassembly. The next prompt will ask "Disassembly with Ascii
Y/N" a 'Y' will cause a note of the Ascii characters represented by
the object code to be made in the remark field. This option is
extremely useful when trying to determine areas of text within a
disassembly.
The final prompt of all is to ask for the name you
wish the generated source files to be called. "D1:" is assumed so
just type in the file name with no extender. A large file will be
broken down into a collection of small manageable files. Each file
will be forty to fifty sectors in length. The first file will be
"D1:TEST.1" followed by "D1:TEST.2" etc. At ten file intervals you
will be asked to insert a blank formatted disk and so on, every ten
files. This prevents nasty disk full errors and gives you some work
space on each disk.
Unfortunately SOURCE WRITER is a little slow at
this stage, so drag out the duster and vacuum and help with the
housework. Do not be disheartened however as you are saving yourself
hours of keyboard work and making a friend of the au pair!
When SOURCE WRITER has finished you will be given
the option of starting another disassembly.
Your limitations? I'm afraid 16k of object code on
a 48k RAM machine. Still that's an awful lot of files.
PROGRAM BREAKDOWN
|
10-60 |
start display |
|
70-190 |
sets
up and initialises strings and arrays |
|
200-280 |
displays options |
|
290-970 |
is
the disassembler and source file writer |
|
980-1100 |
will
read a DOS file into F$ for disassembly |
|
1100-1260 |
will
read a cassette file into F$ |
|
1270-1430 |
will
transfer a specified area of memory into F$ |
|
1440-1610 |
will
load specified sectors into F$ |
|
1620-1720 |
sequentially numbers the source files and prevents disk
overflow |
|
1730-2000 |
is
data for the disassembler |
|
2010 |
is
cassette loader data |
|
2020-2030 |
is the DOS file
loader data. |
|
|
|
 |
