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<article>
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<title>enhanced Apple //e specific information for cc65
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<author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">
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<date>2003-12-16
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<title>Enhanced Apple //e 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 enhanced Apple //e runtime system as it is
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@ -33,48 +33,32 @@ more information.
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<sect>Binary format<p>
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The standard binary output format generated by the linker for the
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enhanced Apple //e target is a machine language program with a 4 byte DOS
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3.3 header containing the load address and load size. The standard load address
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is $803.
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The DOS 3.3 header is in its own segment named <tt/EXEHDR/. If you don't want
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the header for some reason, you can change
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<verb>
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HEADER: start = $0000, size = $0004, file = %O;
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</verb>
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to
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<verb>
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HEADER: start = $0000, size = $0004, file = "";
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</verb>
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in the linker configuration to have the linker remove it.
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The standard binary file format generated by the linker for the
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enhanced Apple //e 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 an option <tt/-cc65/
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that allows to put binary files with the DOS 3.3 header onto disk images
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containing either DOS 3.3 or ProDOS 8.
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Please note that there is an <bf/Apple ][ ProDOS 8 system program
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for loading binary programs/ available in the cc65 User Contributions section.
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It adds all benefits of a ProDOS 8 system program to the standard binary
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program generated by the linker for the enhanced Apple //e target.
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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="apple2enh-4.html#ss4.3" name="apple2enh-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 </-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 35.5KB of RAM are available. While running
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<tt/main()/ the Language Card bank 2 is enabled for read access. However while
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running module constructors/destructors the Language Card is disabled.
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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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@ -82,33 +66,215 @@ Special locations:
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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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Enabling the Language Card allows to use it as additional memory for executable
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code. Actually doing so requires either to compile code with the option
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<tt/--code-name HIGHCODE/ or to use <tt/#pragma codeseg ("HIGHCODE")/.
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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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The amount of memory available in the Language Card for executable code depends
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on the chosen program environment. A plain vanilla ProDOS 8 doesn't actually
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use the Language Card bank 2 memory from $D400 to $DFFF.
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Therefore the builtin linker configuration defines these 3KB as <tt/LC/ memory
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area for executable code.
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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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codeseg (push, "HIGHCODE")/ and <tt/#pragma codeseg (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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A plain vanilla DOS 3.3 doesn't make use of the Language Card at all. So you
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can change
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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="apple2enh-4.html" name="linker configuration">.
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<verb>
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LC: start = $D400, size = $0C00, define = yes;
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</verb>
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to
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<verb>
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LC: start = $D000, size = $3000, define = yes;
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</verb>
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<sect>Linker configurations<p>
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in the linker configuration to define the whole 12KB Language Card address
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space as memory area for executable code.
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The ld65 linker comes with a builtin config file for the enhanced Apple //e,
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which is used via <tt/-t apple2enh/ (and displayed via <tt/--dump-config apple2enh/).
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The apple2enh 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/apple2enh-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/apple2enh-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/apple2enh-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 adress $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/apple2enh-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 adress $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="apple2enh-4.html#ss4.4" name="apple2enh-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 successully linked as system program using the linker
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configuration <htmlurl url="apple2enh-4.html#ss4.3" name="apple2enh-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 apple2enh package comes with the alternative ProDOS 8 I/O buffer allocation
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module <tt/apple2enh-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/apple2enh-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/apple2enh-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 apple2enh -C apple2enh-system.cfg myprog.c apple2enh-iobuf-0800.o
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</verb></tscreen>
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@ -118,7 +284,7 @@ Programs containing enhanced Apple //e specific code may use the
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<tt/apple2enh.h/ header file.
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<sect1>enhanced Apple //e specific functions<p>
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<sect1>Enhanced Apple //e specific functions<p>
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The functions listed below are special for the enhanced Apple //e. See
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the <htmlurl url="funcref.html" name="function reference"> for declaration and
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@ -158,7 +324,7 @@ you cannot do it, it just means that there's no help.
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<tt/--start-addr $6000/ to reserve both hires pages.
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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 executing <tt/_heapadd ((void *) 0x0803, 0x17FD);/
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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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@ -257,7 +423,7 @@ BASIC.SYSTEM) there are some limitations for DOS 3.3:
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Although <htmlurl url="dio.html" name="DIO"> generally works with all ProDOS 8
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devices, the function <htmlurl url="dio-3.html" name="dio_query_sectcount()">
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simply always return 280 (which is only correct for a 140KB disk).
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simply always return 280 (which is only correct for a 140 KB disk).
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<sect1>Direct console I/O<p>
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