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543 lines
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543 lines
17 KiB
Plaintext
<!doctype linuxdoc system>
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<article>
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<title>Apple ][ specific information for cc65
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<author>Oliver Schmidt, <htmlurl url="mailto:ol.sc@web.de" name="ol.sc@web.de">
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<date>2009-10-07
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<abstract>
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An overview over the Apple ][ runtime system as it is
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implemented for the cc65 C compiler.
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</abstract>
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<!-- Table of contents -->
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<toc>
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<!-- Begin the document -->
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<sect>Overview<p>
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This file contains an overview of the Apple ][ runtime system
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as it comes with the cc65 C compiler. It describes the memory layout,
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Apple ][ specific header files, available drivers, and any
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pitfalls specific to that platform.
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Please note that Apple ][ specific functions are just mentioned
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here, they are described in detail in the separate <htmlurl url="funcref.html"
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name="function reference">. Even functions marked as "platform dependent" may
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be available on more than one platform. Please see the function reference for
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more information.
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<sect>Binary format<p>
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The standard binary file format generated by the linker for the
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Apple ][ target is a binary program with a 4 byte DOS 3.3 header
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containing the load address and load length. The default load address is
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$803.
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<bf/AppleCommander 1.3.5/ or later (available at <url
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url="http://applecommander.sourceforge.net/">) includes the option <tt/-cc65/
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that allows to put binary files with a DOS 3.3 header onto disk images
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containing DOS 3.3 as well as ProDOS 8.
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For ProDOS 8 system programs the load address is fixed to $2000 so there
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is no need for a header. Thus the linker configuration
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<htmlurl url="apple2-4.html#ss4.3" name="apple2-system.cfg"> for those programs
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omits the DOS 3.3 header. The right AppleCommander option to put system files
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without a header on a ProDOS 8 disk image is <tt/-p/.
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<sect>Memory layout<p>
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In the standard setup, cc65 generated programs use the memory from
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$803 to $95FF, so 35.5 KB of RAM are available.
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Special locations:
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<descrip>
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<tag/Stack/
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The C runtime stack is located at HIMEM and grows downwards, regardless of
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how your linker config file is setup.
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<tag/Heap/
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The C heap is located at the end of the program and grows towards the C
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runtime stack.
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</descrip><p>
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While running <tt/main()/ the Language Card bank 2 is enabled for read access.
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However while running module constructors/destructors the Language Card is disabled.
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Enabling the Language Card allows to use it as additional memory for cc65
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generated code. However code is never automatically placed there. Rather code
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needs to be explicitly placed in the Language Card either per file by compiling
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with <tt/--code-name HIGHCODE/ or per function by enclosing in <tt/#pragma
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code-name (push, "HIGHCODE")/ and <tt/#pragma code-name (pop)/. In either case the
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cc65 runtime system takes care of actually moving the code into the Language
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Card.
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The amount of memory available in the Language Card for generated code depends
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on the chosen <htmlurl url="apple2-4.html" name="linker configuration">.
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<sect>Linker configurations<p>
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The ld65 linker comes with a builtin config file for the Apple ][,
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which is used via <tt/-t apple2/ (and displayed via <tt/--dump-config apple2/).
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The apple2 package comes with additional secondary linker config files, which
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are used via <tt/-C <configfile>/.
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<sect1>builtin config file<p>
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Default configuration optimized for a binary program running on ProDOS 8 with
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BASIC.SYSTEM. A plain vanilla ProDOS 8 doesn't actually use the Language Card
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bank 2 memory from $D400 to $DFFF.
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<descrip>
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<tag><tt/RAM:/ Main memory area</tag>
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From $803 to $95FF (35.5 KB)
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<tag><tt/LC:/ Language Card memory area</tag>
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From $D400 to $DFFF (3 KB)
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<tag><tt/STARTADDRESS:/ Program start address</tag>
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Variable (default: $803)
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<tag><tt/HEADER:/ Binary file header</tag>
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DOS 3.3 header (address and length)
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</descrip><p>
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<sect1><tt/apple2-dos33.cfg/<p>
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Configuration optimized for a binary program running on DOS 3.3. A plain
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vanilla DOS 3.3 doesn't make use of the Language Card at all.
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<descrip>
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<tag><tt/RAM:/ Main memory area</tag>
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From $803 to $95FF (35.5 KB)
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<tag><tt/LC:/ Language Card memory area</tag>
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From $D000 to $FFFF (12 KB)
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<tag><tt/STARTADDRESS:/ Program start address</tag>
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Variable (default: $803)
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<tag><tt/HEADER:/ Binary file header</tag>
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DOS 3.3 header (address and length)
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</descrip><p>
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<sect1><tt/apple2-system.cfg/<p>
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Configuration for a system program running on ProDOS 8.
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<descrip>
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<tag><tt/RAM:/ Main memory area</tag>
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From $2000 to $BEFF (39.75 KB)
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<tag><tt/LC:/ Language Card memory area</tag>
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From $D400 to $DFFF (3 KB)
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<tag><tt/STARTADDRESS:/ Program start address</tag>
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Fixed ($2000)
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<tag><tt/HEADER:/ Binary file header</tag>
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None
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</descrip><p>
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<sect1><tt/apple2-loader.cfg/<p>
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Configuration optimized for a binary program running on ProDOS 8 without
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BASIC.SYSTEM. Intended to be used with <bf/LOADER.SYSTEM - an
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Apple ][ ProDOS 8 loader for cc65 programs/, which is available
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in the cc65 User Contributions section.
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A program loaded by LOADER.SYSTEM works like a ProDOS 8 system program but
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isn't tied to the start address $2000. Thus with the default start
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address $800 the main memory area is increased by 6 KB.
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<descrip>
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<tag><tt/RAM:/ Main memory area</tag>
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From $800 to $BEFF (45.75 KB)
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<tag><tt/LC:/ Language Card memory area</tag>
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From $D400 to $DFFF (3 KB)
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<tag><tt/STARTADDRESS:/ Program start address</tag>
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Variable (default: $800)
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<tag><tt/HEADER:/ Binary file header</tag>
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DOS 3.3 header (address and length)
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</descrip><p>
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<sect1><tt/apple2-reboot.cfg/<p>
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Configuration optimized for a binary program running on ProDOS 8 without
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BASIC.SYSTEM. Intended to be used with <bf/LOADER.SYSTEM - an
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Apple ][ ProDOS 8 loader for cc65 programs/ (see above) together
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with the function <tt/rebootafterexit()/.
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If a ProDOS 8 system program doesn't quit to the ProDOS 8 dispatcher but rather
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reboots the machine after exit then a plain vanilla ProDOS 8 doesn't make use of
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the Language Card bank 2 at all.
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This setup makes nearly 50 KB available to a cc65 program - on a 64 KB machine!
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<descrip>
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<tag><tt/RAM:/ Main memory area</tag>
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From $800 to $BEFF (45.75 KB)
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<tag><tt/LC:/ Language Card memory area</tag>
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From $D000 to $DFFF (4 KB)
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<tag><tt/STARTADDRESS:/ Program start address</tag>
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Variable (default: $800)
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<tag><tt/HEADER:/ Binary file header</tag>
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DOS 3.3 header (address and length)
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</descrip><p>
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<sect>ProDOS 8 system programs<p>
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ProDOS 8 system programs are always loaded to the start address $2000.
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For cc65 programs this means that the 6 KB from $800 to $2000 are
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by default unused. There are however several options to make use of that memory
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range.
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<sect1>LOADER.SYSTEM<p>
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The easiest (and for really large programs in fact the only) way to have a cc65
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program use the memory from $800 to $2000 is to link it as binary
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(as opposed to system) program using the linker configuration
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<htmlurl url="apple2-4.html#ss4.4" name="apple2-loader.cfg"> with start address
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$800 and load it with <bf/LOADER.SYSTEM - an Apple ][
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ProDOS 8 loader for cc65 programs/. The program then works like a system program
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(i.e. quits to the ProDOS dispatcher).
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Using LOADER.SYSTEM is as simple as copying it to the ProDOS 8 directory of the
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program to load under name <program>.SYSTEM as a system program. For
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example the program <tt/MYPROG/ is loaded by <tt/MYPROG.SYSTEM/.
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<sect1>Heap<p>
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If the cc65 program can be successfully linked as system program using the linker
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configuration <htmlurl url="apple2-4.html#ss4.3" name="apple2-system.cfg"> but
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uses the heap either explicitly or implicitly (i.e. by loading a driver) then
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the memory from $800 to $2000 can be added to the heap by calling
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<tt/_heapadd ((void *) 0x0800, 0x1800);/ at the beginning of <tt/main()/.
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<sect1>ProDOS 8 I/O buffers<p>
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ProDOS 8 requires for every open file a page-aligned 1 KB I/O buffer. By default
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these buffers are allocated by the cc65 runtime system on the heap using
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<tt/posix_memalign()/. While this is generally the best solution it means quite
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some overhead for (especially rather small) cc65 programs which do open files
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but don't make use of the heap otherwise.
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The apple2 package comes with the alternative ProDOS 8 I/O buffer allocation
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module <tt/apple2-iobuf-0800.o/ which uses the memory between $800 and
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the program start address for the 1 KB I/O buffers. For system programs (with
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start address $2000) this results in up to 6 I/O buffers and thus up to 6
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concurrently open files.
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While using <tt/_heapadd()/ as described in the section above together with the
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default I/O buffer allocation basically yields the same placement of I/O buffers
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in memory the primary benefit of <tt/apple2-iobuf-0800.o/ is a reduction in code
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size - and thus program file size - of more than 1400 bytes.
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Using <tt/apple2-iobuf-0800.o/ is as simple as placing it on the linker command
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line like this:
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<tscreen><verb>
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cl65 -t apple2 -C apple2-system.cfg myprog.c apple2-iobuf-0800.o
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</verb></tscreen>
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<sect>Platform specific header files<p>
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Programs containing Apple ][ specific code may use the
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<tt/apple2.h/ header file.
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<sect1>Apple ][ specific functions<p>
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The functions listed below are special for the Apple ][. See
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the <htmlurl url="funcref.html" name="function reference"> for declaration and
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usage.
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<itemize>
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<item>_auxtype
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<item>_dos_type
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<item>_filetype
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<item>get_ostype
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<item>rebootafterexit
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<item>ser_apple2_slot
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<item>tgi_apple2_mix
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</itemize>
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<sect1>Hardware access<p>
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There's currently no support for direct hardware access. This does not mean
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you cannot do it, it just means that there's no help.
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<sect>Loadable drivers<p>
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<sect1>Graphics drivers<p>
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<descrip>
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<tag><tt/a2.lo.tgi/</tag>
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This driver features a resolution of 40×48 with 16 colors.
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The function <tt/tgi_apple2_mix()/ allows to activate 4 lines of text. The
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function clears the corresponding area at the bottom of the screen.
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<tag><tt/a2.hi.tgi/</tag>
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This driver features a resolution of 280×192 with 8 colors and two
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hires pages. Note that programs using this driver will have to be linked
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with <tt/--start-addr $4000/ to reserve the first hires page or with
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<tt/--start-addr $6000/ to reserve both hires pages.
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The function <tt/tgi_apple2_mix()/ allows to activate 4 lines of text. The
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function doesn't clear the corresponding area at the bottom of the screen.
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In memory constrained situations the memory from $803 to $1FFF
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can be made available to a program by calling <tt/_heapadd ((void *) 0x0803, 0x17FD);/
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at the beginning of <tt/main()/. Doing so is beneficial even if the program
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doesn't use the the heap explicitly because loading the driver (and in fact
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already opening the driver file) uses the heap implicitly.
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</descrip><p>
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<sect1>Extended memory drivers<p>
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<descrip>
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<tag><tt/a2.auxmem.emd/</tag>
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Gives access to 47.5 KB RAM (190 pages of 256 bytes each) on an Extended
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80-Column Text Card.
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Note that this driver doesn't check for the actual existence of the memory
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and that it doesn't check for ProDOS 8 RAM disk content!
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</descrip><p>
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<sect1>Joystick drivers<p>
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<descrip>
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<tag><tt/a2.stdjoy.joy/</tag>
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Supports up to two standard analog joysticks connected to the game port of
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the Apple ][.
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</descrip><p>
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<sect1>Mouse drivers<p>
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<descrip>
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<tag><tt/a2.stdmou.mou/</tag>
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Driver for the AppleMouse II Card. Searches all Apple II slots
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for an AppleMouse II Card compatible firmware. The default bounding
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box is [0..279,0..191].
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Programs using this driver will have to be linked with <tt/--start-addr $4000/
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to reserve the first hires page if they are intended to run on an
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Apple ][ (in contrast to an Apple //e) because the
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AppleMouse II Card firmware writes to the hires page when initializing
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on that machine.
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Note that the Apple ][ default mouse callbacks support text
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mode only.
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</descrip><p>
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<sect1>RS232 device drivers<p>
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<descrip>
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<tag><tt/a2.ssc.ser/</tag>
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Driver for the Apple II Super Serial Card. Supports up to 19200 baud,
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hardware flow control (RTS/CTS) and interrupt driven receives. Note
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that because of the peculiarities of the 6551 chip transmits are not
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interrupt driven, and the transceiver blocks if the receiver asserts
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flow control because of a full buffer.
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The driver defaults to slot 2. Call <tt/ser_apple2_slot()/ prior to
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<tt/ser_open()/ in order to select a different slot. <tt/ser_apple2_slot()/
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succeeds for all Apple II slots, but <tt/ser_open()/ fails with
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<tt/SER_ERR_NO_DEVICE/ if there's no SSC firmware found in the selected slot.
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</descrip><p>
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<sect>Limitations<p>
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<sect1>DOS 3.3<p>
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Although the standard binaries generated by the linker for the Apple ][
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generally run both on DOS 3.3 (with Applesoft BASIC) and on ProDOS 8 (with
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BASIC.SYSTEM) there are some limitations for DOS 3.3:
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<descrip>
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<tag>Disk File I/O</tag>
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There's no disk file I/O support. Any attempt to use it yields an error with
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<tt/errno/ set to <tt/ENOSYS/. This implicitly means that loadable drivers
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are in general not functional as they depend on disk file I/O. However they
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may be converted to statically linked drivers using the co65 object-file
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converter.
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<tag/Interrupts/
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There's no <tt/interruptor/ support. Any attempt to use it yields the message
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'FAILED TO ALLOC INTERRUPT' on program startup. This implicitly means that
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<tt/a2.stdmou.mou/ and <tt/a2.ssc.ser/ are not functional as they depend on
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interrupts.
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</descrip><p>
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<sect1>Direct console I/O<p>
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<descrip>
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<tag/Color/
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The Apple ][ has no color text mode. Therefore the functions
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<htmlurl url="funcref-205.html" name="textcolor()">,
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<htmlurl url="funcref-68.html" name="bgcolor()"> and
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<htmlurl url="funcref-69.html" name="bordercolor()"> have no effect.
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<tag/Cursor/
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The Apple ][ has no hardware cursor. Therefore the function
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<htmlurl url="funcref-88.html" name="cursor()"> has no effect.
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</descrip><p>
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<sect>Other hints<p>
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<sect1>Passing arguments to the program<p>
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Command line arguments can be passed to <tt/main()/ after BLOAD. Since this is not
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supported by BASIC, the following syntax was chosen:
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<tscreen><verb>
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]CALL2051:REM ARG1 " ARG2 IS QUOTED" ARG3 "" ARG5
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</verb></tscreen>
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<enum>
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<item>Arguments are separated by spaces.
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<item>Arguments may be quoted.
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<item>Leading and trailing spaces around an argument are ignored. Spaces within
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a quoted argument are allowed.
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<item>The first argument passed to <tt/main/ is the program name.
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<item>A maximum number of 10 arguments (including the program name) are
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supported.
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</enum>
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<sect1>Interrupts<p>
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The runtime for the Apple ][ uses routines marked as
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<tt/.INTERRUPTOR/ for ProDOS 8 interrupt handlers. Such routines must be
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written as simple machine language subroutines and will be called
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automatically by the interrupt handler code when they are linked into a
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program. See the discussion of the <tt/.CONDES/ feature in the <htmlurl
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url="ca65.html" name="assembler manual">.
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<sect1>DIO<p>
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<descrip>
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<tag/Drive ID/
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The function <htmlurl url="dio-1.html" name="dio_open()"> has the single
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parameter <tt/device/ to identify the device to be opened. Therefore an
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Apple II slot and drive pair is mapped to that <tt/device/ according
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to the formula
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<tscreen>
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device = slot + (drive - 1) * 8
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</tscreen>
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so that for example slot 6 drive 2 is mapped to <tt/device/ 14.
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<tag/Sector count/
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The function <htmlurl url="dio-3.html" name="dio_query_sectcount()"> returns
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the correct sector count for all ProDOS 8 disks. However for any non-ProDOS 8
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disk it simply always returns 280 (which is only correct for a 140 KB disk).
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This condition is indicated by the <tt/_oserror/ value 82.
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</descrip><p>
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<sect>Bugs/Feedback<p>
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If you have problems using the library, if you find any bugs, or if you're
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doing something interesting with it, I would be glad to hear from you. Feel
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free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
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name="uz@cc65.org">).
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<sect>License<p>
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This software is provided 'as-is', without any expressed or implied
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warranty. In no event will the authors be held liable for any damages
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arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it
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freely, subject to the following restrictions:
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<enum>
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<item> The origin of this software must not be misrepresented; you must not
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claim that you wrote the original software. If you use this software
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in a product, an acknowledgment in the product documentation would be
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appreciated but is not required.
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<item> Altered source versions must be plainly marked as such, and must not
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be misrepresented as being the original software.
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<item> This notice may not be removed or altered from any source
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distribution.
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</enum>
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</article>
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