GS WorldView: January MM
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RDOS: Supplies for SSI Wargamers!

     RDOS, of course, is the infamous OS employed by Strategic Simulations
to aid in copy protecting many an Apple II game, including a large collection
of wargaming classics.

     Though RDOS-based games have been out of print for eons; they
continue to challenge and entertain Apple II strategists. Thanks to deprotection,
they are available to A2 emulator users, too.

     One snag in the enjoyment of many SSI wargames on emulators has
been the difficulty in getting 'blank' images usable for doing game Saves.
On an actual Apple II the Save disk creation program works; on an
emulator, the result is a mess.

     Sage advice posted by MDRipley37 on comp.emulators.apple2 led to
the Apple Emulator's Wargame Pages and the beginnings of a solution. The
trick suggested there is pretty clever. (You copy the game .dsk, rename the
copy, and delete most of the files.) The resulting .dsk seems to work like a
real Save disk except that things hang after the save.

     Another problem with deleting files to make space is that RDOS saves files
and allocates 'blocks' in sequence, like Pascal. Deleting a file does not
change space allocation-- i.e. you get a bunch of variously sized "unused"

     Most of the marked out "unused" slots are too small for the 25k part of a
game save; so, following the method suggested on AEWP seems to be good for
just one Saved game.

     M.M. McFadden's info on RDOS (ref: Computist #52 and rdos11.shk from
ACN Tarnover) helped in finding a way around the problem. You copy the game
disk and wipe the CATALOG sectors except for a copy of the first entry which
identifies the disk as a Save disk-- easy to do on an Apple II+ using Disk
Muncher and Copy II+. Since the disk has nearly no allocated space, RDOS can
create correctly sized slots as games are saved.

     The resulting blank Save diskette was converted to a .dsk and moved to PC.
On the AppleWin emu playing North Atlantic 86 it seems to work just like the
original using diskettes on the Apple II+. (So, I guess it's okay.)

     When playing around with RDOS files on an emu, it's convenient to have a
dsk which boots RDOS and leaves you in BASIC able to use RDOS commands.
A copy of the North Atlantic 86 game dsk was diddled to allow this.

 The file RDOSstuff.zip includes ...

1- a 'blank' SSI wargame Save .dsk image file
2- a bootable RDOS .dsk disk image file
3- a Text file copy of this document

Download RDOSstuff.zip

Use WinZip or a similar utility to unZip RDOSstuff.zip .

'Blank' SSI wargame Save disk
ref: SSIsave.dsk

     This is a nearly blank disk for saving games created
using info from the Apple Emulator's Wargame Pages and
M.M. McFadden.

Bootable RDOS disk
ref: RDOSboot.dsk

     This disk boots RDOS and permits using standard RDOS
commands listed below. Issuing a 'reset' puts you in the
monitor. (Control-C gets you back to BASIC.)

SSI RDOS Information

from: Apple Emulator's Wargame Pages

RDOS 2.1

RDOS 2.1 is one version of SSI's customized
operating system by Roland Gustafson

Memory Map:
  $B100-B2FF : file buffers
  $B300-B679 : code for RDOS commands
  $B67A-B9FF : RDOS subroutines, error messages, etc.
  $BA00-BFFF : DOS 3.2 RWTS (almost unchanged)
The ampersand interpreter begins at $B303.

There are 17 RDOS commands available:

 &CAT : catalogs a disk.  The actual code is read from block 25
         (track 1, sector 12) of the RDOS disk.

 &LOAD "filename" {,addr} : loads a BASIC program. You may specify a
     different load location (formerly poke 103,lo:
     poke 104,hi) for it.

 &RUN "filename" {,addr} : executes a BASIC program.

 &GOTO "filename" {,addr} : "chains" programs.  Variables are saved, the
      new program is loaded, variables are
      restored, and the program is executed.

 &SAVE "filename" : saves the current BASIC program.

 &STORE "filename", addr, len : BSAVES a file.  The DOS 3.3 command
         BSAVE SPUDS, A$300, L$200 would be
         &STORE"SPUDS", 768, 512.

 &RECALL "filename" {,addr} : BLOADS a file.

 &DEF "filename", size : creates a text file SIZE blocks long. Because
  RDOS uses a contiguous file system (like UCSD
  Pascal), it is necessary to determine the size
  of the file before it is written.

 &PRINT "filename" : writes (appends) a text file.

 &READ "filename" : reads a text file.

 &END : terminates reading or writing of text file by printing ASCII
         character $00 (nul).

 &DEL "filename" : deletes a file.

 &LEN : prints the start location and size of the BASIC program in memory,
         and prints the current lomem value

 &D#, nxtcom : changes the drive number.  Must be used in conjuction with
                another command (i.e., &D2, CAT)

 &S#, nxtcom : changes the slot number.  See above.

 &NEW : erase the current program, reset himem, and coldstart basic (like
         DOS 3.3 "FP").

 &USR addr : If a command is not intercepted by RDOS, it is passed on to
              the routine at ADDR. Do not use a comma.

Filenames, addresses, and slot/drive numbers can be variables. It is
perfectly legal to write statments like:

150 &RECALL "SEGMENT" + STR$(SG) + "A", LOC + 5

More RDOS Stuff!

Andy McFadden writes ...

The ProDOS conversion utilities, including the updated version from issue
#85, are available on http://www.fadden.com/ in the Apple II downloads
Little piece of history: I wrote the utilities originally as a curiosity.
I'd bought a book that showed how to disassemble 6502 code with a simple
methodology involving highlighter pens, and wanted something to work on.
So I disassembled the RDOS code, and built a ProDOS version from scratch.
It mostly worked, but it turns out that it wasn't perfect, and some games
that I didn't have didn't work right.  Evin Mulron sent me a letter
through COMPUTIST, asking for help because he wanted a way to trade
saved games that didn't require snail-mailing an RDOS-formatted disk
around.  If the games ran on ProDOS, it would be easy to just send the
saved game files through a BBS (this is pre-WWW).
Issue #85 has detailed instructions for converting about two dozen SSI
games from RDOS to ProDOS, mostly developed by Evin (who had darn near
every SSI game there was).  From my own collection, I managed to get
Operation Market Garden, Computer Ambush, Phantasie, and Ringside Seat all
on one 800K floppy, which is kinda neat since two of those games occupy
more than one 5.25" disk.  Not only are the game files and save files
accessible from ProDOS, the disk swapping is gone.
A similar technique, for which programs are also present on www.fadden.com,
can convert some of the old SSG games to ProDOS.  I have the original
Reach for the Stars and the "1985" wargames on one disk.



From Phoenyx

     Phoenyx did an adaption of the original P8 RDOS by MM McFadden.
It is enhanced with Extra Variables and some code re-organization plus a
few other features. You can find RDOSPLUS on a ShrinkIt whole-disk
archive (.sdk) file along with a Text info file in the Phoenyx collection on
Ground at http://www.apple2.org.za/mirrors/ground.icaen.uiowa.edu/Collections/Phoenyx/ .

Thanks to the Apple Emulator's Wargame Pages
for the background used for this page!

Strategic Simulations Inc. still makes great games.
Click on the icon to visit SSI's web site.




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