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99 lines
3.7 KiB
Markdown
99 lines
3.7 KiB
Markdown
Prog8 - Structured Programming Language for 8-bit 6502/6510 microprocessors
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===========================================================================
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*Written by Irmen de Jong (irmen@razorvine.net)*
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*Software license: GNU GPL 3.0, see file LICENSE*
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This is a structured programming language for the 8-bit 6502/6510 microprocessor from the late 1970's and 1980's
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as used in many home computers from that era. It is a medium to low level programming language,
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which aims to provide many conveniences over raw assembly code (even when using a macro assembler):
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- reduction of source code length
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- easier program understanding (because it's higher level, and more terse)
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- option to automatically run the compiled program in the Vice emulator
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- modularity, symbol scoping, subroutines
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- subroutines have enforced input- and output parameter definitions
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- various data types other than just bytes (16-bit words, floats, strings, 16-bit register pairs)
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- automatic variable allocations, automatic string variables and string sharing
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- constant folding in expressions (compile-time evaluation)
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- automatic type conversions
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- floating point operations
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- abstracting away low level aspects such as ZeroPage handling, program startup, explicit memory addresses
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- breakpoints, that let the Vice emulator drop into the monitor if execution hits them
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- source code labels automatically loaded in Vice emulator so it can show them in disassembly
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- conditional gotos
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- various code optimizations (code structure, logical and numerical expressions, ...)
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It is mainly targeted at the Commodore-64 machine at this time.
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Required tools:
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---------------
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`64tass <https://sourceforge.net/projects/tass64/>`_ - cross assembler. Install this on your shell path.
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A recent .exe version of this tool for Windows can be obtained from my `clone <https://github.com/irmen/64tass/releases>`_ of this project.
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For other platforms it is very easy to compile it yourself (make ; make install).
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A **Java runtime (jre or jdk), version 8 or newer** is required to run the packaged compiler.
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If you want to build it from source, you'll need a Kotlin 1.3 SDK as well (or for instance,
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IntelliJ IDEA with the Kotlin plugin).
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It's handy to have a C-64 emulator or a real C-64 to run the programs on. The compiler assumes the presence
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of the `Vice emulator <http://vice-emu.sourceforge.net/>`_.
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Example code
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------------
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When this code is compiled::
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%import c64lib
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%import c64utils
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%import c64flt
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~ main {
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sub start() {
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; set text color and activate lowercase charset
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c64.COLOR = 13
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c64.VMCSB |= 2
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; use optimized routine to write text
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c64scr.print("Hello!\n")
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; use iteration to write text
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str question = "How are you?\n"
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for ubyte char in question
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c64.CHROUT(char)
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; use indexed loop to write characters
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str bye = "Goodbye!\n"
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for ubyte c in 0 to len(bye)
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c64.CHROUT(bye[c])
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float clock_seconds = ((mkword(c64.TIME_LO, c64.TIME_MID) as float)
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+ (c64.TIME_HI as float)*65536.0)
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/ 60
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float hours = floor(clock_seconds / 3600)
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clock_seconds -= hours*3600
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float minutes = floor(clock_seconds / 60)
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clock_seconds = floor(clock_seconds - minutes * 60.0)
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c64scr.print("system time in ti$ is ")
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c64flt.print_f(hours)
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c64.CHROUT(':')
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c64flt.print_f(minutes)
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c64.CHROUT(':')
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c64flt.print_f(clock_seconds)
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c64.CHROUT('\n')
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}
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}
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you get a program that outputs this when loaded on a C-64:
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