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367 lines
11 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>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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<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 output format generated by the linker for the
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Apple ][ 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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<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 Apple ][ target.
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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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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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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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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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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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<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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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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<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>_dos_type
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<item>get_ostype
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<item>rebootafterexit
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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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<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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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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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_ioctl(0, <slot>)/ prior to
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<tt/ser_open()/ in order to select a different slot. <tt/ser_ioctl()/
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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</tag>
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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>DIO<p>
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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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<sect1>Direct console I/O<p>
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<descrip>
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<tag>Color</tag>
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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</tag>
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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 <tt/.CONDES/
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type <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 automatically
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by the interrupt handler code when they are linked into a program. See the
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discussion of the <tt/.CONDES/ feature in the <htmlurl url="ca65.html"
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name="assembler manual">.
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<sect1>DIO<p>
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The function <htmlurl url="dio-1.html" name="dio_open()"> has the single parameter
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<tt/drive_id/ to identify the drive to be opened. Therefore an Apple II
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slot and drive pair is mapped to that <tt/drive_id/ according to the formula
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<verb>
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drive_id = (slot * 2) + (drive - 1)
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</verb>
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so that for example slot 6 drive 1 is mapped to <tt/drive_id/ 12.
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The function <htmlurl url="dio-1.html" name="dio_open()"> succeeds only if a
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formatted disk is present in the drive. However intentionally no check is
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performed on the presence of a ProDOS 8 disk. Therefore access to all standard
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16-sector disks (as for instance DOS 3.3) is possible.
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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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