BBC Micro cassette Elite | BBC Micro disc Elite | 6502 Second Processor Elite | BBC Master Elite | Acorn Electron Elite | NES Elite | Elite-A | Teletext Elite | Elite Universe Editor | Elite Compendium | Elite over Econet | Flicker-free Commodore 64 Elite | BBC Micro Aviator | BBC Micro Revs | Archimedes Lander
This repository contains the original source code for Angus Duggan's Elite-A on the BBC Micro, with every single line documented and (for the most part) explained.
It is a companion to the bbcelite.com website.
See the introduction for more information, or jump straight into the documented source code.
This repository contains the original source code for Angus Duggan's Elite-A on the BBC Micro.
You can build the fully functioning game from this source. Three variants are currently supported: the officially released version from Angus's site, the variant produced by the original source discs (which was never released), and a variant that fixes various bugs and which works on the BBC Master (which the original doesn't).
It is a companion to the bbcelite.com website, which contains all the code from this repository, but laid out in a much more human-friendly fashion. The links at the top of this page will take you to repositories for the other versions of Elite that are covered by this project.
Elite-A is legendary amongst BBC Elite fans, and remains a deeply impressive project that has achieved almost mythical status in the Acorn retro scene (and deservedly so). Ian Bell, co-author of the original Elite, has this to say on his website:
Also available here is Angus Duggan's Elite-A, a comprehensive enhancement of BBC Elite. He created this by disassembling the object code and then reprogramming the resultant source. A significant achievement for which respect is due.
It's worth noting that Angus coded Elite-A back in the late 1980s, using a BBC Micro fitted with his own handwritten 6502 assembler ROM, which he used to disassemble the original, protected game binaries, and reassemble the enhanced version. He used Acornsoft's VIEW word processor as his IDE, and built the whole thing without the benefit of modern tooling. A significant achievement, indeed.
I am very grateful to Angus for giving me permission to analyse his work on Elite-A, and for providing me with the original source files.
See Angus's Elite-A site for more information on playing Elite-A.
My hope is that this repository and the accompanying website will be useful for those who want to learn more about Elite and what makes it tick. It is provided on an educational and non-profit basis, with the aim of helping people appreciate one of the most iconic games of the 8-bit era.
Elite-A was written by Angus Duggan, and is an extended version of the BBC Micro disc version of Elite; the extra code is copyright Angus Duggan. The original Elite was written by Ian Bell and David Braben and is copyright © Acornsoft 1984.
The code on this site is identical to Angus Duggan's source discs (it's just been reformatted, and the label names have been changed to be consistent with the sources for the original BBC Micro disc version on which it is based).
The commentary is copyright © Mark Moxon. Any misunderstandings or mistakes in the documentation are entirely my fault.
Huge thanks are due to Angus Duggan for giving me permission to document his work in extending Elite; to the original authors of Elite for not only creating such an important piece of my childhood, but also for releasing the source code for us to play with; to Paul Brink for his annotated disassembly; and to Kieran Connell for his BeebAsm version, which I forked as the original basis for this project. You can find more information about this project in the accompanying website's project page.
This repository is not provided with a licence, and there is intentionally no LICENSE file provided.
According to GitHub's licensing documentation, this means that "the default copyright laws apply, meaning that you retain all rights to your source code and no one may reproduce, distribute, or create derivative works from your work".
The reason for this is that my commentary is intertwined with the original Elite source code, and the original source code is copyright. The whole site is therefore covered by default copyright law, to ensure that this copyright is respected.
Under GitHub's rules, you have the right to read and fork this repository... but that's it. No other use is permitted, I'm afraid.
My hope is that the educational and non-profit intentions of this repository will enable it to stay hosted and available, but the original copyright holders do have the right to ask for it to be taken down, in which case I will comply without hesitation. I do hope, though, that along with the various other disassemblies and commentaries of this source, it will remain viable.
If you want to browse the source in an IDE, you might find the following useful.
-
The most interesting files are in the main-sources folder:
-
The main game's source code is in the elite-source-flight.asm, elite-source-docked.asm and elite-source-encyclopedia.asm files (for when we're in-flight, docked or viewing the encyclopedia) - this is the motherlode and probably contains all the stuff you're interested in.
-
The 6502 Second Processor version's source code is in the elite-6502sp-parasite.asm file (for the parasite, i.e. the Second Processor) and elite-6502sp-io-processor.asm (for the I/O processor, i.e. the BBC Micro).
-
The game's loader is in the elite-loader.asm file - this is mainly concerned with setup and checking for Tube and BBC Master hardware.
-
-
The source files for Elite-A are unique amongst the annotated versions in this project, in that they contain inline diffs. Angus created Elite-A by taking the original disc version of Elite and modifying the code to include all his new features. The annotated source files in this repository contain both the original disc code and all of Angus's modifications, so you can look through the source to see exactly what Angus changed in order to create Elite-A. Any code that he removed from the disc version is commented out in the source files, so when they are assembled they produce the Elite-A binaries, while still containing details of Angus's modifications. You can find all the diffs by searching the sources for
Mod:. (Note that this feature does not apply to the two 6502 Second Processor version source files, which just contain the Elite-A code.) -
It's probably worth skimming through the notes on terminology and notations on the accompanying website, as this explains a number of terms used in the commentary, without which it might be a bit tricky to follow at times (in particular, you should understand the terminology I use for multi-byte numbers).
-
The accompanying website contains a number of "deep dive" articles, each of which goes into an aspect of the game in detail. Routines that are explained further in these articles are tagged with the label
Deep dive:and the relevant article name. -
There are loads of routines and variables in Elite - literally hundreds. You can find them in the source files by searching for the following:
Type: Subroutine,Type: Variable,Type: WorkspaceandType: Macro. -
If you know the name of a routine, you can find it by searching for
Name: <name>, as inName: SCAN(for the 3D scanner routine) orName: LL9(for the ship-drawing routine). -
The entry point for the main game code is routine
TT170, which you can find by searching forName: TT170. If you want to follow the program flow all the way from the title screen around the main game loop, then you can find a number of deep dives on program flow on the accompanying website. -
The source code is designed to be read at an 80-column width and with a monospaced font, just like in the good old days.
I hope you enjoy exploring the inner workings of Elite-A as much as I have.
There are five main folders in this repository, which reflect the order of the build process.
-
1-source-files contains all the different source files, such as the main assembler source files, image binaries, fonts, boot files and so on.
-
2-build-files contains build-related scripts, such as the checksum, encryption and crc32 verification scripts.
-
3-assembled-output contains the output from the assembly process, when the source files are assembled and the results processed by the build files.
-
4-reference-binaries contains the correct binaries for each variant, so we can verify that our assembled output matches the reference.
-
5-compiled-game-discs contains the final output of the build process: an SSD disc image that contains the compiled game and which can be run on real hardware or in an emulator.
This repository also includes a flicker-free version, which incorporates the backported flicker-free ship-drawing routines from the BBC Master. The flicker-free code is in a separate branch called flicker-free, and apart from the code differences for reducing flicker, this branch is identical to the main branch and the same build process applies.
The annotated source files in the flicker-free branch contain both the original Elite-A code and all of the modifications for flicker-free Elite, so you can look through the source to see exactly what's changed. Any code that I've removed from the original version is commented out in the source files, so when they are assembled they produce the flicker-free binaries, while still containing details of all the modifications. You can find all the diffs by searching the sources for Mod:.
For more information on flicker-free Elite, see the hacks section of the accompanying website.
Builds are supported for both Windows and Mac/Linux systems. In all cases the build process is defined in the Makefile provided.
You will need the following to build Elite-A from the source:
-
BeebAsm, which can be downloaded from the BeebAsm repository. Mac and Linux users will have to build their own executable with
make code, while Windows users can just download thebeebasm.exefile. -
Python. The build process has only been tested on 3.x, but 2.7 should work.
-
Mac and Linux users may need to install
makeif it isn't already present (for Windows users,make.exeis included in this repository).
Let's look at how to build Elite-A from the source.
For Windows users, there is a batch file called make.bat which you can use to build the game. Before this will work, you should edit the batch file and change the values of the BEEBASM and PYTHON variables to point to the locations of your beebasm.exe and python.exe executables. You also need to change directory to the repository folder (i.e. the same folder as make.bat).
All being well, entering the following into a command window:
make.bat
will produce a file called elite-a-released.ssd in the 5-compiled-game-discs folder that contains the released version of Elite-A, which you can then load into an emulator, or into a real BBC Micro using a device like a Gotek.
The build process uses a standard GNU Makefile, so you just need to install make if your system doesn't already have it. If BeebAsm or Python are not on your path, then you can either fix this, or you can edit the Makefile and change the BEEBASM and PYTHON variables in the first two lines to point to their locations. You also need to change directory to the repository folder (i.e. the same folder as Makefile).
All being well, entering the following into a terminal window:
make
will produce a file called elite-a-released.ssd in the 5-compiled-game-discs folder that contains the released version of Elite-A, which you can then load into an emulator, or into a real BBC Micro using a device like a Gotek.
By default the build process will create a typical Elite game disc with a standard commander and verified binaries. There are various arguments you can pass to the build to change how it works. They are:
-
variant=<name>- Build the specified variant:variant=released(default)variant=source-discvariant=bug-fix
-
commander=max- Start with a maxed-out commander (specifically, this is the test commander file from the original source, which is almost but not quite maxed-out) -
verify=no- Disable crc32 verification of the game binaries
So, for example:
make variant=bug-fix commander=max verify=no
will build the bug-fix variant with a maxed-out commander and no crc32 verification.
See below for more on the verification process.
The default build process prints out checksums of all the generated files, along with the checksums of the files from the original sources. You can disable verification by passing verify=no to the build.
The Python script crc32.py in the 2-build-files folder does the actual verification, and shows the checksums and file sizes of both sets of files, alongside each other, and with a Match column that flags any discrepancies.
The binaries in the 4-reference-binaries folder were taken straight from Angus Duggan's original source discs, while those in the 3-assembled-output folder are produced by the build process. For example, if you don't make any changes to the code and build the project with make, then this is the output of the verification process:
Results for variant: released
[--originals--] [---output----]
Checksum Size Checksum Size Match Filename
-----------------------------------------------------------
26ae1732 19997 26ae1732 19997 Yes 1.D.bin
b1447e60 16778 b1447e60 16778 Yes 1.E.bin
14ee8b20 17432 14ee8b20 17432 Yes 1.F.bin
3d638042 1956 3d638042 1956 Yes 2.H.bin
1f1783e7 43141 1f1783e7 43141 Yes 2.T.bin
171ccea5 5363 171ccea5 5363 Yes ELITE.bin
4f2febe4 256 4f2febe4 256 Yes MISSILE.bin
678c1c7f 2560 678c1c7f 2560 Yes S.A.bin
cae56eda 2560 cae56eda 2560 Yes S.B.bin
7b56fbb5 2560 7b56fbb5 2560 Yes S.C.bin
55e86dde 2560 55e86dde 2560 Yes S.D.bin
be2665dd 2560 be2665dd 2560 Yes S.E.bin
c0917c15 2560 c0917c15 2560 Yes S.F.bin
80f4145e 2560 80f4145e 2560 Yes S.G.bin
0d9fe4e8 2560 0d9fe4e8 2560 Yes S.H.bin
31ea0782 2560 31ea0782 2560 Yes S.I.bin
f444274e 2560 f444274e 2560 Yes S.J.bin
b9672969 2560 b9672969 2560 Yes S.K.bin
05f74f36 2560 05f74f36 2560 Yes S.L.bin
39856010 2560 39856010 2560 Yes S.M.bin
132980ad 2560 132980ad 2560 Yes S.N.bin
26525e5c 2560 26525e5c 2560 Yes S.O.bin
76097753 2560 76097753 2560 Yes S.P.bin
6bd215b4 2560 6bd215b4 2560 Yes S.Q.bin
bcd49589 2560 bcd49589 2560 Yes S.R.bin
8b44b8b6 2560 8b44b8b6 2560 Yes S.S.bin
155e6a6b 2560 155e6a6b 2560 Yes S.T.bin
fab17499 2560 fab17499 2560 Yes S.U.bin
8504604f 2560 8504604f 2560 Yes S.V.bin
40f96e61 2560 40f96e61 2560 Yes S.W.bin
b7b3c692 1024 b7b3c692 1024 Yes WORDS.bin
All the compiled binaries match the originals, so we know we are producing the same final game as the released version.
During compilation, details of every step are output in a file called compile.txt in the 3-assembled-output folder. If you have problems, it might come in handy, and it's a great reference if you need to know the addresses of labels and variables for debugging (or just snooping around).
For users of the excellent b2 emulator, you can include the build parameter b2 to automatically load and boot the assembled disc image in b2. The b2 emulator must be running for this to work.
For example, to build, verify and load the game into b2, you can do this on Windows:
make.bat all b2
or this on Mac/Linux:
make all b2
If you omit the all target then b2 will start up with the results of the last successful build.
Note that you should manually choose the correct platform in b2 (I intentionally haven't automated this part to make it easier to test across multiple platforms).
This repository contains the source code for three different variants of Elite-A:
-
The released version from Angus Duggan's site
-
The variant produced by the source disc (which was never released)
-
A variant that fixes two bugs in the original (splinters and Adder stats)
By default the build process builds the released version, but you can build a specified variant using the variant= build parameter.
You can add variant=released to produce the elite-a-released.ssd file that contains the released version, though that's the default value so it isn't necessary. In other words, you can build it like this:
make.bat variant=released
or this on a Mac or Linux:
make variant=released
This will produce a file called elite-a-released.ssd in the 5-compiled-game-discs folder that contains the released version.
The verification checksums for this version are as follows:
Results for variant: released
[--originals--] [---output----]
Checksum Size Checksum Size Match Filename
-----------------------------------------------------------
26ae1732 19997 26ae1732 19997 Yes 1.D.bin
b1447e60 16778 b1447e60 16778 Yes 1.E.bin
14ee8b20 17432 14ee8b20 17432 Yes 1.F.bin
3d638042 1956 3d638042 1956 Yes 2.H.bin
1f1783e7 43141 1f1783e7 43141 Yes 2.T.bin
171ccea5 5363 171ccea5 5363 Yes ELITE.bin
4f2febe4 256 4f2febe4 256 Yes MISSILE.bin
678c1c7f 2560 678c1c7f 2560 Yes S.A.bin
cae56eda 2560 cae56eda 2560 Yes S.B.bin
7b56fbb5 2560 7b56fbb5 2560 Yes S.C.bin
55e86dde 2560 55e86dde 2560 Yes S.D.bin
be2665dd 2560 be2665dd 2560 Yes S.E.bin
c0917c15 2560 c0917c15 2560 Yes S.F.bin
80f4145e 2560 80f4145e 2560 Yes S.G.bin
0d9fe4e8 2560 0d9fe4e8 2560 Yes S.H.bin
31ea0782 2560 31ea0782 2560 Yes S.I.bin
f444274e 2560 f444274e 2560 Yes S.J.bin
b9672969 2560 b9672969 2560 Yes S.K.bin
05f74f36 2560 05f74f36 2560 Yes S.L.bin
39856010 2560 39856010 2560 Yes S.M.bin
132980ad 2560 132980ad 2560 Yes S.N.bin
26525e5c 2560 26525e5c 2560 Yes S.O.bin
76097753 2560 76097753 2560 Yes S.P.bin
6bd215b4 2560 6bd215b4 2560 Yes S.Q.bin
bcd49589 2560 bcd49589 2560 Yes S.R.bin
8b44b8b6 2560 8b44b8b6 2560 Yes S.S.bin
155e6a6b 2560 155e6a6b 2560 Yes S.T.bin
fab17499 2560 fab17499 2560 Yes S.U.bin
8504604f 2560 8504604f 2560 Yes S.V.bin
40f96e61 2560 40f96e61 2560 Yes S.W.bin
b7b3c692 1024 b7b3c692 1024 Yes WORDS.bin
You can build the source disc variant by appending variant=source-disc to the make command, like this on Windows:
make.bat variant=source-disc
or this on a Mac or Linux:
make variant=source-disc
This will produce a file called elite-a-from-source-disc.ssd in the 5-compiled-game-discs folder that contains the source disc variant.
The verification checksums for this version are as follows:
Results for variant: source-disc
[--originals--] [---output----]
Checksum Size Checksum Size Match Filename
-----------------------------------------------------------
d1ca0224 19997 d1ca0224 19997 Yes 1.D.bin
b1447e60 16778 b1447e60 16778 Yes 1.E.bin
14ee8b20 17432 14ee8b20 17432 Yes 1.F.bin
3d638042 1956 3d638042 1956 Yes 2.H.bin
81d6d436 43141 81d6d436 43141 Yes 2.T.bin
171ccea5 5363 171ccea5 5363 Yes ELITE.bin
4f2febe4 256 4f2febe4 256 Yes MISSILE.bin
678c1c7f 2560 678c1c7f 2560 Yes S.A.bin
cae56eda 2560 cae56eda 2560 Yes S.B.bin
7b56fbb5 2560 7b56fbb5 2560 Yes S.C.bin
55e86dde 2560 55e86dde 2560 Yes S.D.bin
be2665dd 2560 be2665dd 2560 Yes S.E.bin
c0917c15 2560 c0917c15 2560 Yes S.F.bin
80f4145e 2560 80f4145e 2560 Yes S.G.bin
0d9fe4e8 2560 0d9fe4e8 2560 Yes S.H.bin
31ea0782 2560 31ea0782 2560 Yes S.I.bin
f444274e 2560 f444274e 2560 Yes S.J.bin
b9672969 2560 b9672969 2560 Yes S.K.bin
05f74f36 2560 05f74f36 2560 Yes S.L.bin
39856010 2560 39856010 2560 Yes S.M.bin
132980ad 2560 132980ad 2560 Yes S.N.bin
26525e5c 2560 26525e5c 2560 Yes S.O.bin
76097753 2560 76097753 2560 Yes S.P.bin
6bd215b4 2560 6bd215b4 2560 Yes S.Q.bin
bcd49589 2560 bcd49589 2560 Yes S.R.bin
8b44b8b6 2560 8b44b8b6 2560 Yes S.S.bin
155e6a6b 2560 155e6a6b 2560 Yes S.T.bin
fab17499 2560 fab17499 2560 Yes S.U.bin
8504604f 2560 8504604f 2560 Yes S.V.bin
40f96e61 2560 40f96e61 2560 Yes S.W.bin
b7b3c692 1024 b7b3c692 1024 Yes WORDS.bin
You can build the source disc variant by appending variant=bug-fix to the make command, like this on Windows:
make.bat variant=bug-fix
or this on a Mac or Linux:
make variant=bug-fix
This will produce a file called elite-a-bug-fix.ssd in the 5-compiled-game-discs folder that contains the bug fix variant.
The verification checksums for this version are as follows:
Results for variant: bug-fix
[--originals--] [---output----]
Checksum Size Checksum Size Match Filename
-----------------------------------------------------------
d733f7f3 19997 d733f7f3 19997 Yes 1.D.bin
cd68d57e 16796 cd68d57e 16796 Yes 1.E.bin
14ee8b20 17432 14ee8b20 17432 Yes 1.F.bin
07b3750f 2008 07b3750f 2008 Yes 2.H.bin
f02c9501 43094 f02c9501 43094 Yes 2.T.bin
067375d2 5385 067375d2 5385 Yes ELITE.bin
4f2febe4 256 4f2febe4 256 Yes MISSILE.bin
678c1c7f 2560 678c1c7f 2560 Yes S.A.bin
cae56eda 2560 cae56eda 2560 Yes S.B.bin
7b56fbb5 2560 7b56fbb5 2560 Yes S.C.bin
55e86dde 2560 55e86dde 2560 Yes S.D.bin
a119f0d9 2560 a119f0d9 2560 Yes S.E.bin
c0917c15 2560 c0917c15 2560 Yes S.F.bin
d3224bc1 2560 d3224bc1 2560 Yes S.G.bin
0d9fe4e8 2560 0d9fe4e8 2560 Yes S.H.bin
31ea0782 2560 31ea0782 2560 Yes S.I.bin
f444274e 2560 f444274e 2560 Yes S.J.bin
ad98f535 2560 ad98f535 2560 Yes S.K.bin
05f74f36 2560 05f74f36 2560 Yes S.L.bin
39856010 2560 39856010 2560 Yes S.M.bin
132980ad 2560 132980ad 2560 Yes S.N.bin
a258d111 2560 a258d111 2560 Yes S.O.bin
76097753 2560 76097753 2560 Yes S.P.bin
6bd215b4 2560 6bd215b4 2560 Yes S.Q.bin
2aefc58b 2560 2aefc58b 2560 Yes S.R.bin
8b44b8b6 2560 8b44b8b6 2560 Yes S.S.bin
155e6a6b 2560 155e6a6b 2560 Yes S.T.bin
22336ce1 2560 22336ce1 2560 Yes S.U.bin
8504604f 2560 8504604f 2560 Yes S.V.bin
40f96e61 2560 40f96e61 2560 Yes S.W.bin
b7b3c692 1024 b7b3c692 1024 Yes WORDS.bin
You can see the differences between the variants by searching the source code for _RELEASED (for features in the released version), _BUG_FIX (for features in the buf fix version) or _SOURCE_DISC (for features in the source disc variant).
The only difference in the source disc variant is that the latter has considerably lower ship prices.
The bug fix variant works on the BBC Master and BBC Master with 6502 Second Processor, which the original version of Elite-A doesn't. There is also a bug in the original version that prevents splinters from displaying properly, which makes mining all but impossible. The bug fix variant fixes that bug, and it also adds a quality-of-life improvement to the cargo capacities shown for flyable ships in the encyclopedia, so they reflect the in-game capacity when no equipment is fitted, rather than the "normal configuration" from the original version (which is a bit subjective).
See the accompanying website for a comprehensive list of differences between the variants.
See the original source files for details about how Angus's original sources have been converted to assemble in BeebAsm, so Elite-A can be built on modern computers.
Right on, Commanders!
Mark Moxon