BBC Micro cassette Elite | BBC Micro disc Elite | Acorn Electron Elite | 6502 Second Processor Elite | Commodore 64 Elite | Apple II Elite | BBC Master Elite | NES Elite | Elite-A | Teletext Elite | Elite Universe Editor | Elite Compendium (BBC Master) | Elite Compendium (BBC Micro) | Elite over Econet | Flicker-free Commodore 64 Elite | BBC Micro Aviator | BBC Micro Revs | Archimedes Lander
This repository contains the original source code for the cassette version of Elite on the BBC Micro, with every single line documented and (for the most part) explained. It is literally the original source code, just heavily commented.
It is a companion to the elite.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 the cassette version of Elite on the BBC Micro, with every single line documented and (for the most part) explained.
You can build the fully functioning game from this source. Three variants are currently supported: the tape version from the Stairway to Hell archive, the version produced by the original source discs from Ian Bell's personal website, and the version built from the text sources from the same site.
This repository is a companion to the elite.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.
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If you want to browse the source and read about how Elite works under the hood, you will probably find the website a better place to start than this repository.
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If you would rather explore the source code in your favourite IDE, then the annotated source is what you're looking for. It contains the exact same content as the website, so you won't be missing out (the website is generated from the source files, so they are guaranteed to be identical). You might also like to read the section on browsing the source in an IDE for some tips.
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If you want to build BBC Micro cassette Elite from the source on a modern computer, to produce a working game disc that can be loaded into a BBC Micro or an emulator, then you want the section on building BBC Micro cassette Elite from the source.
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.
BBC Micro Elite was written by Ian Bell and David Braben and is copyright © Acornsoft 1984.
The code on this site is identical to the source discs released on Ian Bell's personal website (it's just been reformatted to be more readable).
The commentary is copyright © Mark Moxon. Any misunderstandings or mistakes in the documentation are entirely my fault.
Huge thanks are due to the original authors 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.
Thank you to Diminished for the UEF scripts, which are part of the Quadbike 2 tape transcriber.
The following archives from Ian Bell's personal website form the basis for this project:
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.
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The most interesting files are in the main-sources folder:
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The main game's source code is in the elite-source.asm file - this is the motherlode and probably contains all the stuff you're interested in.
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The game's loader is in the elite-loader.asm file - this is mainly concerned with setup and copy protection.
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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).
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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 BBC Elite as much as I have.
There are five main folders in this repository, which reflect the order of the build process.
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1-source-files contains all the different source files, such as the main assembler source files, image binaries, fonts, boot files and so on.
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2-build-files contains build-related scripts, such as the checksum, encryption and crc32 verification scripts.
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3-assembled-output contains the output from the assembly process, when the source files are assembled and the results processed by the build files.
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4-reference-binaries contains the correct binaries for each variant, so we can verify that our assembled output matches the reference.
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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 Acornsoft 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.
This repository also includes a version of BBC Micro cassette Elite for the Elite Compendium, which incorporates all the available hacks in one game. The Compendium version is in a separate branch called elite-compendium, which is included in the Elite Compendium (BBC Micro) repository as a submodule.
The annotated source files in the elite-compendium branch contain both the original Acornsoft code and all of the modifications for the Elite Compendium, 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 Compendium 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 the Elite Compendium, 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 BBC Micro cassette Elite from the source:
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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 might work.
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Mac and Linux users may need to install
makeif it isn't already present (for Windows users,make.exeis included in this repository).
For details of how the build process works, see the build documentation on bbcelite.com.
Let's look at how to build BBC Micro cassette Elite 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-cassette-sth.ssd in the 5-compiled-game-discs folder that contains the source disc variant, 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-cassette-sth.ssd in the 5-compiled-game-discs folder that contains the source disc variant, 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:
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variant=<name>- Build the specified variant:variant=sth(default)variant=source-discvariant=text-sources
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disc=no- Build a version to load from cassette rather than disc (the default is to build a version that loads from disc) -
protect=no- When building for cassette withdisc=no, the loader contains block-level tape protection code, which you can disable with this argument (the protection only works if you save the ELITEcode file to tape with corrupted block data, so if you want to create a UEF without re-implementing the Acornsoft protection system, you should use this argument) -
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) -
encrypt=no- Disable encryption and checksum routines -
verify=no- Disable crc32 verification of the game binaries
So, for example:
make variant=text-sources commander=max encrypt=no match=no verify=no
will build an unencrypted text sources variant with a maxed-out commander, no workspace noise and no crc32 verification.
The unencrypted version should be more useful for anyone who wants to make modifications to the game code. As this argument produces unencrypted files, the binaries produced will be quite different to the binaries on the original source disc, which are encrypted.
See below for more on the verification process.
If you change the source code in any way, you may break the game; if so, it will typically hang at the loading screen, though in some versions it may hang when launching from the space station.
To fix this, you may need to update some of the hard-coded addresses in the checksum script so that they match the new addresses in your changed version of the code. See the comments in the elite-checksum.py script for details.
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. If you are building an unencrypted set of files then there will be lots of differences, while the encrypted files should mostly match (see the Differences section below for more on this).
The binaries in the 4-reference-binaries folder were taken straight from the cassette sources disc image, 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: sth
[--originals--] [---output----]
Checksum Size Checksum Size Match Filename
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a88ca82b 5426 a88ca82b 5426 Yes ELITE.bin
f40816ec 5426 f40816ec 5426 Yes ELITE.unprot.bin
b17f9589 2228 b17f9589 2228 Yes ELTA.bin
82de44f7 2600 82de44f7 2600 Yes ELTB.bin
f005a7bf 2732 f005a7bf 2732 Yes ELTC.bin
ac3476d9 2887 ac3476d9 2887 Yes ELTD.bin
3084f112 2663 3084f112 2663 Yes ELTE.bin
e46bac22 2719 e46bac22 2719 Yes ELTF.bin
b4ac917d 2340 b4ac917d 2340 Yes ELTG.bin
b1bf493e 20712 b1bf493e 20712 Yes ELTcode.bin
33de34f5 20712 33de34f5 20712 Yes ELTcode.unprot.bin
00d5bb7a 40 00d5bb7a 40 Yes ELThead.bin
99529ca8 256 99529ca8 256 Yes PYTHON.bin
49ee043c 2502 49ee043c 2502 Yes SHIPS.bin
c4547e5e 1023 c4547e5e 1023 Yes WORDS9.bin
All the compiled binaries match the originals, so we know we are producing the same final game as the Stairway to Hell variant.
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).
Despite this being the cassette version of BBC Micro Elite, this repository only builds disc images by default, as that's how BeebAsm works. If you want the authentic experience of loading Elite from cassette, then you can build a UEF with the following command on Windows:
make.bat uef disc=no protect=no
or this on Mac/Linux:
make uef disc=no protect=no
You should now be able to load Elite from your UEF on a BBC Micro, by entering CHAIN "ELITE". These UEF tape images will work with emulators and the TZXDuino (though you may need to unzip them before they will work with the latter).
For this to work, you will need PHP installed, and you should edit the Makefile (and make.bat on Windows) to point to PHP (specifically, you'll need to point the PHP variable to point to the locations of your php or php.exe binary).
Note that in order for your UEF to work, you need to include the disc=no and protect=no arguments to the build (as above). This ensures that the binaries are built to load at the correct address for tape systems, and it also disables the block-level tape protection system, as this only works with specially created tape images, like the ones that Acornsoft originally released.
This repository contains the source code for three different variants of the cassette version of Elite:
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The variant from the Stairway to Hell archive
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The variant produced by the original source discs from Ian Bell's personal website
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The variant built from the text sources from the same site
By default the build process builds the Stairway to Hell variant, but you can build a specified variant using the variant= build parameter.
You can add variant=source-disc to produce the elite-cassette-from-source-disc.ssd file containing the source disc variant, though that's the default value so it isn't necessary. In other words, you can build it like this:
make.bat variant=sth
or this on a Mac or Linux:
make variant=sth
This will produce a file called elite-cassette-sth.ssd in the 5-compiled-game-discs folder that contains the Stairway to Hell variant.
The verification checksums for this version are as follows:
Results for variant: sth
[--originals--] [---output----]
Checksum Size Checksum Size Match Filename
-----------------------------------------------------------
a88ca82b 5426 a88ca82b 5426 Yes ELITE.bin
f40816ec 5426 f40816ec 5426 Yes ELITE.unprot.bin
b17f9589 2228 b17f9589 2228 Yes ELTA.bin
82de44f7 2600 82de44f7 2600 Yes ELTB.bin
f005a7bf 2732 f005a7bf 2732 Yes ELTC.bin
ac3476d9 2887 ac3476d9 2887 Yes ELTD.bin
3084f112 2663 3084f112 2663 Yes ELTE.bin
e46bac22 2719 e46bac22 2719 Yes ELTF.bin
b4ac917d 2340 b4ac917d 2340 Yes ELTG.bin
b1bf493e 20712 b1bf493e 20712 Yes ELTcode.bin
33de34f5 20712 33de34f5 20712 Yes ELTcode.unprot.bin
00d5bb7a 40 00d5bb7a 40 Yes ELThead.bin
99529ca8 256 99529ca8 256 Yes PYTHON.bin
49ee043c 2502 49ee043c 2502 Yes SHIPS.bin
c4547e5e 1023 c4547e5e 1023 Yes WORDS9.bin
Note that if you add the disc=no build parameter, then the build will produce binaries that are designed to be loaded from cassette rather than disc. The verification step will compare the results to the exact binaries from the UEF from the Stairway to Hell archive. These binaries have block-level tape protection enabled by default, so they will not match. You can override the block-level protection with protect=no.
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-cassette-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
-----------------------------------------------------------
a88ca82b 5426 a88ca82b 5426 Yes ELITE.bin
f40816ec 5426 f40816ec 5426 Yes ELITE.unprot.bin
0f1ad255 2228 0f1ad255 2228 Yes ELTA.bin
e725760a 2600 e725760a 2600 Yes ELTB.bin
97e338e8 2735 97e338e8 2735 Yes ELTC.bin
322b174c 2882 322b174c 2882 Yes ELTD.bin
29f7b8cb 2663 29f7b8cb 2663 Yes ELTE.bin
8a4cecc2 2721 8a4cecc2 2721 Yes ELTF.bin
7a6a5d1a 2340 7a6a5d1a 2340 Yes ELTG.bin
01a00dce 20712 01a00dce 20712 Yes ELTcode.bin
1e4466ec 20712 1e4466ec 20712 Yes ELTcode.unprot.bin
00d5bb7a 40 00d5bb7a 40 Yes ELThead.bin
99529ca8 256 99529ca8 256 Yes PYTHON.bin
49ee043c 2502 49ee043c 2502 Yes SHIPS.bin
c4547e5e 1023 c4547e5e 1023 Yes WORDS9.bin
You can build the text sources variant by appending variant=text-sources to the make command, like this on Windows:
make.bat variant=text-sources
or this on a Mac or Linux:
make variant=text-sources
This will produce a file called elite-cassette-from-text-sources.ssd in the 5-compiled-game-discs folder that contains the Ian Bell disc variant.
The verification checksums for this version are as follows:
Results for variant: text-sources
[--originals--] [---output----]
Checksum Size Checksum Size Match Filename
-----------------------------------------------------------
093c73aa 5426 093c73aa 5426 Yes ELITE.bin
24da3246 5426 24da3246 5426 Yes ELITE.unprot.bin
6c109c76 2228 6c109c76 2228 Yes ELTA.bin
cd8bee0c 2600 cd8bee0c 2600 Yes ELTB.bin
20c22628 2732 20c22628 2732 Yes ELTC.bin
23c13c71 2885 23c13c71 2885 Yes ELTD.bin
ce0d9ec7 2663 ce0d9ec7 2663 Yes ELTE.bin
5aed3c61 2719 5aed3c61 2719 Yes ELTF.bin
13f3eace 2340 13f3eace 2340 Yes ELTG.bin
8b79fe39 20710 8b79fe39 20710 Yes ELTcode.bin
7c24aab0 20712 7c24aab0 20712 Yes ELTcode.unprot.bin
00d5bb7a 40 00d5bb7a 40 Yes ELThead.bin
99529ca8 256 99529ca8 256 Yes PYTHON.bin
8f4b6f2b 2502 8f4b6f2b 2502 Yes SHIPS.bin
c4547e5e 1023 c4547e5e 1023 Yes WORDS9.bin
You can see the differences between the variants by searching the source code for _STH_CASSETTE (for features in the Stairway to Hell variant), _SOURCE_DISC (for features in the source disc variant) or _TEXT_SOURCES (for features in the text sources variant). There are only minor differences:
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The text sources contain an extra call in the galactic hyperspace routine that sets the current system to the nearest system to the crosshairs, in an attempt to fix a bug in the original source disc variant (though it doesn't quite fix it properly).
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The Stairway to Hell variant contains the extra call in the galactic hyperspace routine, but in a different place, and it also zeroes the distance to the current system in QQ8. This fixes the galactic hyperspace bug properly, and this full bug fix is present in all other versions of the game.
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In order to fit in this extra call, the text sources and Stairway to Hell variants also contain modifications to create space for the call.
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There is a small change in the TTX66 routine to reset LAS2 to 0 instead of LASCT to stop laser pulsing, as this is slightly more efficient.
See the accompanying website for a comprehensive list of differences between the variants.
It also turns out there are two versions of the ELITEB BASIC source program on the cassette sources disc image, one called $.ELITEB and another called O.ELITEB. These two versions of ELITEB differ by just one byte in the default commander data. This byte controls whether or not the commander has a rear pulse laser. In O.ELITEB this byte is generated by:
EQUB (POW + 128) AND Q%
while in $.ELITEB, this byte is generated by:
EQUB POW
The BASIC variable Q% is a Boolean flag that, if TRUE, will create a default commander with lots of cash and equipment, which is useful for testing. You can see this in action if you build an unencrypted binary with make build, as the unencrypted build sets Q% to TRUE for this build target.
The BASIC variable POW has a value of 15, which is the power of a pulse laser. POW + 128, meanwhile, is the power of a beam laser.
Given the above, we can see that O.ELITEB correctly produces a default commander with no a rear laser if Q% is FALSE, but adds a rear beam laser if Q% is TRUE. This matches the default commander from the released game, and produces the ELTcode executable on the same disc. The version of ELITEB in the cassette sources as text files matches this version, O.ELITEB.
In contrast, $.ELITEB will always produce a default commander with a rear pulse laser, irrespective of the setting of Q%, so it doesn't match the released version.
The ELTB binary file in the 4-reference-binaries folder of this repository matches the version generated by the source disc, so we can easily tell whether any changes we've made to the code deviate from this version. However, the ELTB binary file on the sources disc matches the version produced by $.ELITEB, rather than the version produced by O.ELITEB - in other words, ELTB on the source disc is not the version generated by the source code on the same disc.
The implication is that the ELTB binary file on the cassette sources disc image was produced by $.ELITEB, while the ELTcode file (the released game) used O.ELITEB. Perhaps the released game was compiled, and then someone backed up the ELITEB source to O.ELITEB, edited the $.ELITEB to have a rear pulse laser, and then generated a new ELTB binary file. Who knows? Unfortunately, files on DFS discs don't have timestamps, so it's hard to tell.
Right on, Commanders!
Mark Moxon