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THE GEEK SITE.

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6502 CROSS COMPILER: 1998-

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Screen shot of a demo program compiled with Quetzalcoatl.
Yep; that's right! Bitmapped graphics on a VIC!

Click here to download the Quetzalcoatl Compiler.

Compilers are perhaps the most elegant of all computer programs.

I wrote Quetzalcoatl becaused I wanted to write a
full-blown compiler and linker from scratch!

News:
October 30, 2006: Online Forum for Quetzalcoatl Questions and Suggested Changes.
This replaces e-mail which had become flooded by spam, spam, spam
October 13, 2006: MacOS Port by Harry, MasterMind Game.

October 9, 2006: GNU Public License Source Release. The Quetzalcoatl Source has
now been released under GPL. A big thanks to Harry Dodgson, who did a lot of
work on Quetzalcoatl in 2005. This is version 2.1.0 BETA, as in Beta Release. It
includes many bug fixes and improvements by Harry. I've also updated the
Compiler Hacker's Guide (CHG). I would have liked to have added textbook quality
comments, but I simply don't have time. Instead I've commented the headers and
some of the source bodies. Along with the CHG, I hope this is enough for
would-be compiler hackers. The CHG contains suggestions for what function still
needs to be added, and a tutorial on optimisation. You can download the source
from here here. Enjoy!

May 30, 2001: Congratulations Mike Dailly for taking the 6502 Challenge. This
will be smaller next release. By request, here's the very-rough programmers
manual in HTML. The Quetzalcoatl Source code is being released on request.
Here's the Quetzalcoatl Compiler Hacker's Guide. The latest version of
Quetzalcoatl (not yet on this web site) has double-byte support. What does this
mean? Among other things, that you can write your programs in East-Asian
languages. Not immediately useful perhaps, but nice to know it's there if you
need it. :-)
September 15, 1999: The Quetzalcoatl Source Code is (finally) released!
June 14, 1999: To date, there have been 147 downloads of Quetzalcoatl: 39 for
Linux, 84 for DOS and 106 for Windows. (Some people grab more than one port,
thus the overlap.) I have been bugged for the source by 1 (count 'em!) person. I
haven't had time to do any more work on the new version, so structs will have to
wait! :( If anyone has the time, energy and naivity ;) to take this on
themselves, let me know! Quetzacoatl is written in C++ and uses an LL(1) parser;
(Not LR(1)! Automatically generated compilers are for wimps!)
March 10, 1999: Quetzalcoatl's Source will be released under GNU once enough
people have bugged me to do so.
February 5, 1999: Found the pointer bug. It turned out to be a minor problem
with scoping. To workaround it include brackets in your pointer references
within expressions: *x = (*x) + 3
December 15, 1998: Several people have reported using Quetzalcoatl as a 6502
assembler; This is fine! For standalone assembler programs call your main
routine "main:". Here's a brief note I prepared describing how to call assembler
routines from C. The next release of Quetzalcoatl will add pointers and
relocatable assembler modules. I plan to release the Quetzalcoatl Source Code
under GNU sometime 1999, after I've had a chance to tidy up and properly
document the code.
October 4, 1998: Version 2.0a4 is out, with the Commodore 64 port, limited C
pointers and assembly listing files. Quetzalcoatl now lets you edit bitmapped
graphics or your own programmable character set and link them directly into the
executable!
September 25, 1998: Once were a 6502 warrior? See if you can squeeze a few more
bytes out of the 6502 assembly runtime library.
September 24, 1998: The Alpha Release is out! The keyword here is "Alpha". It
may still contain bugs, and the documentation is incomplete. If you don't feel
up to this wait for the beta. The Alpha version is here.



WHAT IS QUETZALCOATL

Quetzalcoatl is a Cross Compiler for 6502 Processors. Quetzalcoatl runs under
Win32, Linux, Solaris, DOS and MacOS. It can compile and link programs written
in a subset of ANSI C called Tiny C, Assembler, the 1983 UPL language or any
combination thereof. It is suitable for producing programs for the Commodore
VIC-20 and Commodore 64. (You can run executables directly on emulators such as
PCVIC or Free-64). With some minor modifications Quetzalcoatl will also produce
code for the Apple ][, old 6502 game consoles (such as the Nintendo
Entertainment System) and 6502 embedded systems.

Quetzalcoatl began as an experiment in compiler optimisation. Although it was
not originally planned to be released publicly, the result was a decent "C"
Compiler that could benefit the 6502 retrocomputing community. Accordingly
Quetzalcoatl is being released free for non-commercial use.


WHAT IS QUETZALCOATL'S DEVELOPMENT STATUS?

The 6502 Assembler and Tiny C (arrays, subroutines, integer math) is complete.
Adding structs, multi-level pointers, classes and more optimisations are
suggested projects. Because Quetzalcoatl is an LL(1) compiler, it is easier and
more interesting / educational than e.g. YACC generated compilers. See the
Compiler Hacker's Guide.

The Alpha version was completed in 1998, and the Beta in 2006.

 * Signed and unsigned 8 and 16 bit data-types, complete with 16 bit
   multiplication and division.
 * Arrays, enumerated types, Pointers. TODO: Structures.
 * Procedures and Functions.
 * Built-in Console I/O. You can add your own sound and graphics I/O.
   
 * A Full 6502 Assembler, which you can use standalone for any 6502 machine; VIC
   and Commodore 64 are ready to go.
 * Modular, relocatable object code.
 * Optimisation.
 * Small Memory Footprint; Quetzalcoatl code is already quite compact.
   * (Given the target machine can only have 3.5Kb of RAM, it'd have to be! :-)

Since Quetzalcoatl's target systems generally have very little memory and few
spare cycles it's unlikely you'll see Quetzalcoatl turn into bloatware. Future
releases of Quetzalcoatl will focus on further optimisation, rather than adding
advanced language features.

Extensions such as graphics and sound interfaces for particular platforms can be
written as application modules, linked in only when needed. This site will
maintain an archive for any such modules you write and want to share with other
developers. As provided Quetzalcoatl restricts its platform-dependent code to
the runtime library. Even within it there is very little platform-dependent code
anyway; So much so that console I/O executables for the VIC-20 actually run on
the Commodore 64 without modification!


HOW EFFICIENT IS QUETZALCOATL?

Quetzalcoatl was developed as a test-bed for experimenting with native code
optimisation. Accordingly, the code that is produced is already reasonably
efficient. In later releases it will become even moreso. The 6502 was an ideal
target for this experiment, because it is far from being an ideal processor!

Quetzalcoatl has a tiny runtime library; just over 1Kb, allowing it to squeeze
onto just about anything. Quetzalcoatl comes with a full-blown linker that can
select smaller versions of the runtime library, based on whatever functions you
happen to use. The source of the runtime library is also distributed with
Quetzalcoatl, allowing developers to produce even smaller custom versions or
ports for other platforms.

What is UPL?

UPL is an old language developed in 1983. Although Quetzalcoatl began as a UPL
compiler, it very quickly became a C compiler. I wouldn't recommend anybody use
UPL today. You can do everything it can do and much more with C.


WHAT DOES QUETZALCOATL COST?

Quetzalcoatl is free for non-commercial use.

Why does Quetzalcoatl have such a strange name?

I think you already know the answer to this. J


HOW DO I GET QUETZALCOATL?

Quetzalcoatl is available here. This lists the 1998 Alpha version for various
platforms, and the 2006 Beta GPL source release. Why so long between releases?
Lack of time! Hard to earn a living from 6502 coding these days! ;-)




WHERE IS THE QUETZALCOATL DOCUMENTATION?

Click here for

 * A very-rough programmer's manual. A copy of this is included in Adobe Acrobat
   PDF format within the base distribution.
 * The Compiler hackers guide (for modifying the actual compiler).



Author. 

Quetzalcoatl has been developed by Brendan Jones in his spare (hah!) time.




LINKS.

 * CC65 is a mature 6502 C compiler (based on an Atari 8 bit compiler), ported
   to the Commodore 64 and 128. CC65 is at the ANSI C level, including support
   for structs which Quetzalcoatl currently lacks.
 * BJ's VIC-20 software, including the old 1983 UPL Compiler written in BASIC!

 

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© Brendan Jones, 1998. All Rights Reserved. Quetzalcoatl is a trademark of
Kestrel Defence.
Created: August 20, 1998.