prog8/README.md

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Prog8 - Structured Programming Language for 8-bit 6502/65c02 microprocessors
============================================================================
*Written by Irmen de Jong (irmen@razorvine.net)*
*Software license: GNU GPL 3.0, see file LICENSE*
This is a structured programming language for the 8-bit 6502/6510/65c02 microprocessor from the late 1970's and 1980's
as used in many home computers from that era. It is a medium to low level programming language,
which aims to provide many conveniences over raw assembly code (even when using a macro assembler).
Documentation
-------------
Full documentation (syntax reference, how to use the language and the compiler, etc.) can be found at:
https://prog8.readthedocs.io/
What does Prog8 provide?
------------------------
- reduction of source code length over raw assembly
- fast execution speed due to compilation to native assembly code. It's possible to write certain raster interrupt 'demoscene' effects purely in Prog8.
- modularity, symbol scoping, subroutines
- various data types other than just bytes (16-bit words, floats, strings)
- Strings can contain excaped characters but also many symbols directly if they have a petscii equivalent, such as "♠♥♣♦π▚●○╳". Characters like ^, _, \, {, } and | are also accepted and converted to the closest petscii equivalents.
- automatic static variable allocations, automatic string and array variables and string sharing
- subroutines with input parameters and result values
- high-level program optimizations
- small program boilerplate/compilersupport overhead
- Programs can be run multiple times without reloading because of automatic variable (re)initializations.
- conditional branches
- floating point operations (requires the C64 Basic ROM routines for this)
- 'when' statement to provide a concise jump table alternative to if/elseif chains
- many built-in functions such as ``sin``, ``cos``, ``rnd``, ``abs``, ``min``, ``max``, ``sqrt``, ``msb``, ``rol``, ``ror``, ``swap``, ``sort`` and ``reverse``
- various powerful built-in libraries to do I/O, number conversions, graphics and more
- convenience abstractions for low level aspects such as ZeroPage handling, program startup, explicit memory addresses
- inline assembly allows you to have full control when every cycle or byte matters
- supports the sixteen 'virtual' 16-bit registers R0 .. R15 from the Commander X16, and provides them also on the C64.
- encode strings and characters into petscii or screencodes as desired (C64/Cx16)
*Rapid edit-compile-run-debug cycle:*
- use a modern PC to do the work on, use nice editors and enjoy quick compilation times
- can automatically run the program in the Vice emulator after succesful compilation
- breakpoints, that let the Vice emulator drop into the monitor if execution hits them
- source code labels automatically loaded in Vice emulator so it can show them in disassembly
*Two supported compiler targets* (contributions to improve these or to add support for other machines are welcome!):
- "c64": Commodore-64 (6510 CPU = almost a 6502)
- "cx16": [CommanderX16](https://www.commanderx16.com) (65c02 CPU)
- If you only use standard kernal and prog8 library routines, it is possible to compile the *exact same program* for both machines (just change the compiler target flag)!
Additional required tools
-------------------------
[64tass](https://sourceforge.net/projects/tass64/) - cross assembler. Install this on your shell path.
A recent .exe version of this tool for Windows can be obtained from my [clone](https://github.com/irmen/64tass/releases) of this project.
For other platforms it is very easy to compile it yourself (make ; make install).
A **Java runtime (jre or jdk), version 11 or newer** is required to run a prepackaged version of the compiler.
If you want to build it from source, you'll need a Java SDK + Kotlin 1.3.x SDK (or for instance,
IntelliJ IDEA with the Kotlin plugin).
It's handy to have an emulator (or a real machine perhaps!) to run the programs on. The compiler assumes the presence
of the [Vice emulator](http://vice-emu.sourceforge.net/) for the C64 target,
and the [x16emu emulator](https://github.com/commanderx16/x16-emulator) for the CommanderX16 target.
Example code
------------
This code calculates prime numbers using the Sieve of Eratosthenes algorithm::
%import textio
%zeropage basicsafe
main {
ubyte[256] sieve
ubyte candidate_prime = 2 ; is increased in the loop
sub start() {
sys.memset(sieve, 256, false) ; clear the sieve
txt.print("prime numbers up to 255:\n\n")
ubyte amount=0
repeat {
ubyte prime = find_next_prime()
if prime==0
break
txt.print_ub(prime)
txt.print(", ")
amount++
}
txt.nl()
txt.print("number of primes (expected 54): ")
txt.print_ub(amount)
txt.nl()
}
sub find_next_prime() -> ubyte {
while sieve[candidate_prime] {
candidate_prime++
if candidate_prime==0
return 0 ; we wrapped; no more primes
}
; found next one, mark the multiples and return it.
sieve[candidate_prime] = true
uword multiple = candidate_prime
while multiple < len(sieve) {
sieve[lsb(multiple)] = true
multiple += candidate_prime
}
return candidate_prime
}
}
when compiled an ran on a C-64 you'll get:
![c64 screen](docs/source/_static/primes_example.png)
One of the included examples (wizzine.p8) animates a bunch of sprite balloons and looks like this:
![wizzine screen](docs/source/_static/wizzine.png)
Another example (cube3d-sprites.p8) draws the vertices of a rotating 3d cube:
![cube3d screen](docs/source/_static/cube3d.png)
If you want to play a video game, a fully working Tetris clone is included in the examples:
![tehtriz_screen](docs/source/_static/tehtriz.png)
There are a couple of examples specially made for the CommanderX16 compiler target.
For instance here's a well known space ship animated in 3D with hidden line removal,
in the CommanderX16 emulator:
![cobra3d](docs/source/_static/cobra3d.png)