Contents of the RESOURCE.DOC file
A disassembler for 8080 programs
by Ward Christensen
Modified for HDOS by Cliff Kimmery
Modified to support PIC files 7/26/82
The command summary at the end is the only
portion of this file which has been changed
to reflect the HDOS version.
Documentation copied to PC from HDOS to provide
information on program operation.
CP/M U.G. 1/80
Suggestions? Call me eve's at (312) 849-6279
RESOURCE commands are inconsistent at best. - RESOURCE is a
kludge based on years of disassembler experience and hacking,
and was never "planned" - just coded sitting at a tube, and
modified over 2 years before being contributed to the CP/M UG.
For example, to kill a symbol: k.label but to kill a
control value: caddr,k and to kill a comment: ;addr,
but RESOURCE does the job like no other I have seen.
N-O-T-E: Pardon the editorial, but I feel hardware without
good software is useless to 99% of us.Most good software
has to be paid for. I strongly support the legitimate purchase
of licensed software. I do not regularly use any programs
which I have not purchased. (Yes, I do occasionally "try"
one, but then buy it if I plan on using it). I have been
asked by software businesses to NOT distribute RESOURCE -
because of it's ability to produce good .asm source quickly.
But, there are so many disassemblers out, why not a good,
conversational one? Please use it in the spirit in which it
was contributed: to enlarge your understanding of the micro-
computer world around you, and to allow you to customize
programs which you legitimately own, for your own use.
"Semper non rippus offus"
NOTE: any command taking a hex address (Dnnnn, etc)
may take a value in the form .label but arithmetic
may not be performed. (i.e. d.start is ok, but d.start+8 not)
Overall structure of RESOURCE:It is a .COM file,
which runs at 100H. It goes thru 1700 or so. then the stack.
At 1800 is a 512 entry table for control commands. Each is
3 bytes long, and controls the format of the re-sourced list,
i.e. is it DB, DS, DW, instructions, etc.
At 1E00 is the start of the symbol table. It has no
defined length as such. If it is not used, it occupies only
If you want to re-source something which is in memory,
such as a PROM, a program previously loaded in high memory,
"CP/M itself", or whatever, you can just do so.
However, typically you want to disassemble a program
which runs at 100H, which is were RESOURCE runs. Bob
Van Valzah would have solved that by making resource
relocatable and moving itself up under BDOS. I wasn't that
Instead, RESOURCE uses the concept of an "invisible"
OFFSET. After all, what do you care where it is as long
as it LOOKS like it's at 100h?
So, you set an offset.O2F00 sets it to 2F00 Hex.
Reading a .COM file (RFOO.COM) causes it to come into 3000 on.
If you say D100 or L100 it dumps or lists what LOOKS like your
program. Internally, RESOURCE is adding the offset to the
D and L addresses.
What should you set the offset to? Well, that depends
upon how many symbols you will use. O1F00 will load the
program at 2000, thus allowing only 1E00-1FFF for symbols,
i.e. 512 bytes or about 50-60 labels. If you didn't leave
enough space, then used B to build a default symbol table,
the table could run into and clobber your .com file! (easy
recovery, however: just change the offset to being higher,
and read in the .COM file again) Each entry takes 3 bytes
+ the symbol length, and if you like 7 byte labels like I
do, that means 10 bytes/label.An offset of 2F00 should
If you want to put comments into the disassembled
program, you will have to designate an area to Use for the
comments. The U command (e.g. U4000) specifies what area
is to be used.
Before issuing the O (offset) command, do:
which will show the JMP to BDOS, which is the highest memory
you may use. (Note if you have, for example, an empty 4K
memory board in high memory, you can Use THAT for comments).
Let's take an example:You have an 8K file, FOO.COM
which you want to disassemble.It will have about 300 labels.
300 x 10 is 3000, or call it 4K (what's a K unless your
tight). The symbol table starts at 1E00. 4K more is 2E00.
Let's load the .COM at 2E00, so since it normally starts
at 100H, the offset is 2D00. O2D00 is the command.
We then RFOO.COM to read it in. It says 4E00 2100 which
means it came into actual memory to 4E00, but 2100 if we
are talking with respect to loading at 100.
Thus, we could set our comments table up after
the .COM program - say at 5000: U5000
The ? command shows the memory utilization for
control, symbol, and comments entries.(no, I never put
in anything to keep track of the .COM - you'll just have
to do that yourself).
If you ever want to dump real memory, you'll have
to reset the offset to 0: O0 but then set it back.
If you are not sure what it is, typing O will tell the
Hoo, boy! Hope this kludge of documentation
is enough to get you going - hmmm, better give you
some of the gotcha's I've discovered...
---- WATCH FOR ----
*Symbols overflowing into the .COM.
(Use ? command to see how full symbol table is)
*Control entries overflowing into .SYM (altho I
can't believe anyone will have a program with
more than 512 control entries!!!)
*Comments overflowing into BDOS (ug!!)
*Using an offset which is not in free memory
and overlaying BDOS or whatever.
*The B(uild) command gobbling up too much when building
a DB: "B" will take a DB 'GOBBELDY GOOK' followed
by LXI H,FOO and take the LXI as a '!' (21H) so
you'll have to manually stick a new "I" control
entry in at the address of the LXI. You might
also delete the incorrect "I" entry which RESOURCE
stuck in (typically at the second byte of the LXI)
*Trying to dump real memory without setting the
offset back to 0. (then forgetting to set it back
to its proper value)
*Forgetting how big the .COM file you are disassembling
*Using RESOURCE to rip off software (yes, I know, you
heard that before, but only 3 in 100 needed to be
told, and 2 in 100 needs to be told again, and 1 in
100 doesn't give a rat's fuzzy behind anyway!!)
*Forgetting to take checkpoints when disassembling
large files. You may even want to rotate the names
under which things are saved:
*Missing a label: Suppose you have a control entry
for a DW, resulting in:
but somewhere in the program, the following exists:
Even if you did a B and have a label L172D, it won't
show up since it's in the middle of a DW. Instead,
K.l172d kill the old label
e172d,.dflt+1put in the new label as a displacement
off the beginning.
*improperly disassembling DW's (see previous item).
You might be tempted to make DFLT a DB so that
Note that while this disassembles and reassembles
properly, it is not "as correct" as the technique
used in the previous item.
*Having the "B" command overlay your "E" control entry.
What? Well, "B"uild is pretty dumb. If he finds 8
DB type characters in a row, he fires off a DB from
then on until he runs out of those characters.Suppose
your program was 200 long (ended at 3FF), and you
had zeroed (aha! Nice DB candidates) memory there
(there meaning at your offset address + whatever).
Then you QB100,400 and viola!!RESOURCE overlaid
your "E" control with a "B".
RESOURCE is relatively complete. (well, actually,
the phrase "rampant featureitis" has been "mentioned").
...But there's always another day, and another K...
SO... Here's my "wish list"
..it might save you telling me YOU think such-and-such
would be nice...
*Targets of LHLD, SHLD should automatically be flagged
as type DW in the control table. Ditto LDA and STA
as DB or as second half of DW. Ditto targets of LXI
as DB (?).
should automatically calculate the appropriate
displacement, and put it in the symbol table.
*The comments facility should be enhanced to allow
total SUBSTITUTION of entire line(s) of the code,
i.e. at address such-and-such, replace the next 3
bytes with the following arbitrary line. This
would help those "how do I explain what was being
done" cases such as:LXIH,BUFFER AND 0FF00H
*Add the ability to, in one instruction, rename
a default (LXXXX) label to a meaningful name.
RESOURCE types an "*" prompt when it is loaded. You may
then enter any of the following commands. Each command
is a single letter followed by operands. Commas are shown
as the delimiter, but a space will also work.
;Put comments into the program.
(must execute 'u' command first, to assign area
for comments to be placed)
;addr,commententer a comment
;addrlists existing comment
;lists entire comments table
;addr,deletes existing comment
note that '\' is treated as a new line, i.e.
\test\ will be formatted:
Attempt to find DB's while listing the program.
-This command works just like 'L', but attempts
to find DB's of 8 chars or longer.
(see 'L' command for operand formats)
Build default sym tbl (LXXXX) labels for each
-2 byte operand encountered. Note 'B' is
identical to 'L' except labels are built.
(see 'L' command for operand formats)
Control table usage:
-cdump ctl tbl
cnnnndump from starting
cnnnn,xdefine format from nnnn
to next entry. values of x:
B = DB (attempts ASCII
printable, 0DH, 0AH, 0)
W = DW (attempts label)
S = DW to next ctl entry
I = instructions
K = kill this ctl entry
E = end of disassembly
NOTE every control entry causes a "control break"
(NO, RESOURCE was NOT written in RPG) which means
a new line will be started. Thus if you have a
string in memory which disassembles as:
You might want to change it putting the 0DH,0AH
together on the second line - just enter a "B"
control entry for the address of the 0DH.
The same technique could be used to make
DB'TYPESAVEDIR ERA REN '
-dxxxxDumps 80H from xxxx on
daaaa,bbbbDumps from aaaa thru bbbb
d,bbbbContinues, thru bbbb
dContinues, 80H more
NOTE 80H is the default dump length. If you have
a larger display, you can change the default via:
d=nnnn is the HEX new default.
For example, a 24 line tube could display 100H:
d=100,200Defaults to 100, dumps 200-2ff
-ennnn,.symbol symbol may be of any length,
and contain any char A-Z or 0-9,
or "+" or "-". This allows:
E5D,.FCB+1. Note the "+" is not
checked, i.e. E5D,.FCB+2 would be
wrong (assuming FCB is at 5C) but
would be allowed to be entered.
Note if you enter two symbols for the same address,
whichever one is first alphabetically will show up
on the disassembled listing. If you have a label
which has the wrong address, you need not explicitly
kill the old one before entering the new. A label
which is spelled exactly the same as an existing one
will replace the existing one even if the addresses
Find occurrence of address or label. Note this function
-runs until interrupted (press any key).
fnnnn,ssssfind address nnnn in memory. Start
the search at ssss. Runs forever.
Press any key to stop.
fcontinue previous find command
fnnnnfind nnnn starting at address you last
stopped at in the f command
kill symbol from table
list (disassemble). This command is used to list the
-file, or to list it to disk after enabling
the .ASM file save via 'SFILENAME.ASM' command
llists 10 lines from prev pc
lssss,eeeelists from ssss to eeee
l,eeeelists from current pc to eeee
lsssslists 10 lines at ssss
Note that if you have a control 'e' entry, then the
list will stop when that address is found. This allows
you to 'lstart,ffff'.
The 10 line default may be changed via:
L=nnwhere nn is a HEX line count, e.g.
L=14set to 20 lines/screen
You can change the default and list, e.g.
L=9,100Dflt to 9 lines, list at 100.
NOTE when using L to list the .ASM program to disk,
you should either list the entire program at once
using: Lssss,eeee or, you can list small pieces
at a time. As long as you list again without
specifying a starting address, (L or L,nnnn) then
the output file will continue uninterrupted.
You may do dump commands, and others, without
affecting what is being written to disk.
offset for disassembly
-oprint current offset
onnnnestablish new offset
(note the offset is always added to any
address specified in an a, b, d, or l command.
to dump real memory, the offset must be reset to
0 (O0) before the dump.)
prolog generation - this routine generates an
-ORG instruction, and equates for any label
outside of a given low-hi address pair.
(the start and end addresses of your program).
e.g. if disassembling from 100 to 3ff, it will
generate 'fcb equ 5ch' if FCB is in the symbol
table. In typical use, you would 'sfilename.asm'
then use the P command to write the prolog, then
the L command to write the program itself.
Pstart addr,end addr
quiet command: any command which is preceeded by a q
-will be done 'quietly'. For example, to save
a .asm program, you could just do:
ql100,3fforql100,ffff if you have
set the 'e' control in the control table.
Another use is to build a default symbol table
by taking a pass thru the program: QB100,xxxx
read .com, .ctl, .sym, or .doc file
-rfilename.comreads in at offset+100h
rfilename.ctlloads the ctl table
rfilename.symloads the sym file
rfilename.docloads the comments table (note
'u' command must have been issued)
save .asm, .ctl, .sym, or .doc file
-sfilename.asmuse 'l' command to write, z to end
sfilename.CTLsaves the CTL table
stablename.symsaves the sym file
sfilename.docsaves the comments table
use area of memory for comments table
-unnnnsuch as ud000 if you had an
open board at 0d000h
purge sym tbl and CTL tbl
close .asm file (note that a preferred way to close the
.asm file is to have specified a control entry
for the end address (e.g. c1ff,e))
Here is a sample of the RESOURCE usage.
Given:a COM file (lets say test.com) which runs at 100
(as any good COM file should), and goes thru 2FF.
lines preceeded with ---> are typed by you.
---> o2200set the offset to 2200, which means the
program will read into 2200 + 100 = 2300.
---> rtest.comreads the com file into memory. system says:
2500 0300 which is the actual hi load addr,
(2500) and the original hi load addr (300)
REMEMBER this address (300) because you might
want to put a "E" (end of assembly) control
<<<>>> that all 'L' (disassembly list) and 'D' (dump)
commands work with the offset added. Thus, you
should learn to forget that the disassembler is
in memory, and think of it as if your program were
actually at 100. D100 will dump your program.
also note: if the program being "RESOURCEd" will
have a fairly large symbol table, then you will
have to set the offset higher: o2f00 or some such.
(the ? command will show symbol table usage: if your
symbol table is nearing the .com file, then just
set a new offset (higher) and re-load the .com)
if you want to dump r-e-a-l memory, you would have
to reset the offset to 0: o0 (but don't forget to
reset it to 1f00 before continuing with your program.)
If you are disassembling something which is in memory at
it's correct address (such as looking at ccp) then don't
set the offset. It defaults to 0 when dis is first loaded.
--->l100list your program - lists "about" 10 lines.
--->d100do a dump of your program.
NOTE that typically here are the steps to disassembling
a program which has just been read into memory:
Use the dump command to find the ASCII DB areas.
Note that the 'a' command may be used to automatically
find the db's, but you must then check them to insure
that they don't extend too far. All printable characters,
0dh, 0ah, and 00h are considered candidates for ascii db's.
At least 8 characters in a row must be found to make sure
that long sequences of mov instructions won't be taken
Use the cnnnn,k command to kill erronious entries put
in the control table by the a command, but then immediately
put in the right address, such as via cnnnn,i
if you wanted to scan the program for ascii db's yourself,
use the 'c' (control) command to set the beginning and
end of ascii areas. For example, a program
which starts out:
would show up in the dump as:
0100 c3170144 4f50xxxx xxxxxxxx xxxxxxxx *...copyr ight....*
0110 xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx *xxxxxxxx ........*
thus you would want to instruct the disassembler to switch
to db mode at 103, and back to instruction mode at 117, thus:
Continue doing this, bracketing every ascii db which is in
the middle of instructions, by a b control instruction
and an i control instruction. Note that multiple db's in
a row need not have separate cnnnn,b instructions, but that
these do cause a 'line break', i.e. if you have a table
of ascii commands, for example:
the disassembler would disassemble these as:
you could put in an additional control entry: c2e9,b, which
would cause the disassembler to generate:
which is much more readable and realistic.
Note that before generating each byte of a db, a symbol
table lookup is done to determine if there is a label
at that location, and if so, a new line is started.
Thus if 'loadlit' and 'savelit' were in the symbol table,
as the labels on the 'load' and 'save' above, no separate
'b' control instruction would be required as the label
would cause the break.
<<<>>> that at this time the automatic label checking
is n-o-t done for ds instructions. Make sure that each
ds instrucion references only up to the next label. This
means that multiple ds's in a row must each be explicitly
entered into the control table. Presence of a label is
After building the control entries with cnnnn,b and cnnnn,i
put in a control entry cnnnn,e which defines the address of
the end of your program. The l command will then automatically
stop there, and in addition, if you are in 'save xxx.asm'
mode, the output .asm file will be closed. If you do
mot define a control 'e' entry, then you will have to use
the break facility to stop the l command (don't use control-c
as that will re-boot cp/m). If you were writing an .asm
file, you would have to user the z command to close the
Next, you would list your program to determine how it looks.
when you recognize a routine by it's function, insert a label.
For example, if you saw that location 7ef was a character
out routine (type) then enter a label into the symbol table:
NOTE that all symbols start with a '.', so as to be dis-
tinguished from hex data.
NOTE that if you want the disassembler to make default labels
for you, use b (for build labels) instead of l (for list
program). The b commands causes lnnnn default labels to
be inserted in the symbol table for every 2 byte operand
encountered (LXI, SHLD, JMP, etc). It will undoubtedly
make some you don't want, such as L0000. You will have to:
K.L0000kill label L0000 from the table.
When you encounter data reference instructions, try
to determine what type of area the instruction points to.
Typically,, LXI instructions may point to a work area
which should be defined as a DS, or to an ASCII string,
in which case we will have already made it a 'b' control
instruction. Operands of LHLD and SHLD instructions
should be made DW instructions. For example if you
encounter LHLD 0534H, then issue a control instruction:
NOTE that whatever mode you are last in will remain in
effect. Therefore if 534,w is the last entry in the
control table, all data from there on will be taken to be
Suppose that you determine that address 7cf is a 128 byte
buffer for disk I/O. You want it to disassemble to:
You do this as follows:
C7CF,Sto start the DS
C84F,Bto define it's end, and
E7CF,.DKBUFto put the symbol in the table.
Continue, iteratively using the 'l' command and the 'c'
and 'e' commands until you have the listing in a nice
format. You will then probably want to save the control
symbol, and comments tables. Or, you could have been
saving them at checkpoint times (so if you make a
major mistake you could go back to a previous one).
To save a control file:
sfilename.CTL(any filename, may include a: or b:)
To save a symbol file:
To save a comments file:
sfilename.doc(not ".com" of course)
NOTE that the filetypes must be used as shown, but
that any legal filename (or disk:filename such as b:xxxx.CTL)
may be used.
You could now control-c to return to CP/M, and come back
later to resume your disassembly:
uxxxx(such as u4000)
This will take you back exactly where you left off.
If you want to save a .asm file out to disk, do the following:
Make sure that there is a control entry defining the end
of the program (such as c200,e) or else you will have to
specify the ending address and manually type a z command to
close the file.
A message will indicate that the file is opened. Any
subsequent a, b, or l command will have whatever is listed
written to disk. Encountering a 'e' control, or typing a z
command will then close the .asm file. The listing may
be interrupted, and continued. Since the l command types
only 10 lines, use laddr,ffff to list thru the end of the
If this is the 'final' save of the .asm file, you will
probably want to put an 'org' at the beginning of the
output file, as well as generate equ instructions for
any references outside of the program. For example, a
typical cp/m program will have references to:
the 'p' (for prologue) command generates the org, then
scans the symbol table and generates equates:
If you have a "e" control entry in your file, you can
list as follows: laddr,ffff - the listing will continue
until the "e" control entry is found
if you entered a label in the symbol table but now want
to get rid of it:
note to rename a symbol, such as when you had a system-
assigned lnnnn label but now want to make it meaningful:
you could even:
but that takes more typing.
here are some more commands:
?prints statistics on symbol and control table
cprints the entire control table
cnnnnprints the control table starting
at address nnnn
dsdumps the symbol table. Interrupt it
by typing any key.
ds.symbolstarts dumping at the specified symbol,
or the nearest symbol.thus "ds.f" starts
the dump at the first label starting
with the letter 'f'.
....have fun, and let me know of any problems or
This is the only portion of the Documentation which
has been modified (for HDOS)-- Cliff Kimmery
"Quick" command summary
Any address may be replaced by .symbol i.e. D.START
Repeats previous single letter command
*addr,commentEnter a comment
*addrLists existing comment
*Lists entire comments table
*addr,Deletes existing comment
@Sort symbol table
.Dumps the symbol table
.symbol Dumps a single symbol
A(see "L" for operands) Attempt to find DB's
B(see "L" for operands) Build default sym tbl (Lxxxx)
CDump ctl tbl
CnnnnDump ctl starting at nnnn
Cnnnn,x Define format from nnnn (B,H,E,I,S,W)
Cnnnn,K Kill ctl entry
DxxxxDumps 80H from xxxx on
Daaaa,bbbbDumps from aaaa thru bbbb
D,bbbbDump thru bbbb
DDump 80H more
D=nnnn= Hex dump size default.
Ennnn,.symbolEnter symbol into table
Fnnnn,ssssFind address nnnn starting at ssss
FContinue previous find command
HHelp with commands
HxHelp with command "x"
Innnn,ooooIncrement every symbol from "nnnn"
on by "oooo"
K.symbolKill symbol from symbol table
LLists 10 lines from prev pc
Lssss,eeeeLists from ssss to eeee
L,eeeeLists from current pc to eeee
LssssLists 10 lines at ssss
L=nnnn is hex list default # of lines
OPrint current offset
OnnnnEstablish new offset
Pstart addr,end addrGenerate program prolog
QBefore any command suppresses
console output: QB100,200
Rfilename.ABSReads in at offset - supports PIC format
Rfilename.DVDReads in at offset - supports PIC format
Rfilename.SYSReads in at offset - supports PIC format
Rfilename.CTLLoads the control table
Rfilename.SYMLoads the symbol table
Rfilename.DOCLoads the comments table
Sfilename.ASMSave .ASM file. Write B/L, Z to end
Sfilename.CTLSaves the control table
Sfilename.SYMSaves the symbol table
Sfilename.DOCSaves the comments table
TnnnnSet starting address of Symbol Table
(Purge to reinitialize end)
UnnnnUse nnnn for comments table
XPurge all symbols and control
ZWrite eof to .ASM file
?Prints statistics (sym, ctl, comments)