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<title>Apple&nbsp;&rsqb;&lsqb; specific information for cc65
<author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">
<date>2003-12-16

<abstract>
An overview over the Apple&nbsp;&rsqb;&lsqb; runtime system as it is
implemented for the cc65 C compiler.
</abstract>

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<sect>Overview<p>

This file contains an overview of the Apple&nbsp;&rsqb;&lsqb; runtime system
as it comes with the cc65 C compiler. It describes the memory layout,
Apple&nbsp;&rsqb;&lsqb; specific header files, available drivers, and any
pitfalls specific to that platform.

Please note that Apple&nbsp;&rsqb;&lsqb; specific functions are just mentioned
here, they are described in detail in the separate <htmlurl url="funcref.html"
name="function reference">. Even functions marked as "platform dependent" may
be available on more than one platform. Please see the function reference for
more information.



<sect>Binary format<p>

The standard binary output format generated by the linker for the
Apple&nbsp;&rsqb;&lsqb; target is a machine language program with a 4 byte DOS
3.3 header containing the load address and load size. The standard load address
is &dollar;803.

The DOS 3.3 header is in its own segment named <tt/EXEHDR/. If you don't want
the header for some reason, you can change

<verb>
    HEADER: start = $0000, size = $0004, file = %O;
</verb>

to

<verb>
    HEADER: start = $0000, size = $0004, file = "";
</verb>

in the linker configuration to have the linker remove it.

<bf/AppleCommander 1.3.5/ or later (available at <url
url="http://applecommander.sourceforge.net/">) includes an option <tt/-cc65/
that allows to put binary files with the DOS 3.3 header onto disk images
containing either DOS 3.3 or ProDOS 8.

Please note that there is an <bf/Apple&nbsp;&rsqb;&lsqb; ProDOS 8 system program
for loading binary programs/ available in the cc65 User Contributions section.
It adds all benefits of a ProDOS 8 system program to the standard binary
program generated by the linker for the Apple&nbsp;&rsqb;&lsqb; target.



<sect>Memory layout<p>

In the standard setup, cc65 generated programs use the memory from
&dollar;803 to &dollar;95FF, so 35.5KB of RAM are available. While running
<tt/main()/ the Language Card bank 2 is enabled for read access. However while
running module constructors/destructors the Language Card is disabled.

Special locations:

<descrip>
  <tag/Stack/
  The C runtime stack is located at HIMEM and grows downwards, regardless of
  how your linker config file is setup.

  <tag/Heap/
  The C heap is located at the end of the program and grows towards the C
  runtime stack.
</descrip><p>

Enabling the Language Card allows to use it as additional memory for executable
code. Actually doing so requires either to compile code with the option
<tt/--code-name HIGHCODE/ or to use <tt/#pragma codeseg ("HIGHCODE")/.

The amount of memory available in the Language Card for executable code depends
on the chosen program environment. A plain vanilla ProDOS 8 doesn't actually
use the Language Card bank 2 memory from &dollar;D400 to &dollar;DFFF.
Therefore the builtin linker configuration defines these 3KB as <tt/LC/ memory
area for executable code.

A plain vanilla DOS 3.3 doesn't make use of the Language Card at all. So you
can change

<verb>
    LC: start = $D400, size = $0C00, define = yes;
</verb>

to

<verb>
    LC: start = $D000, size = $3000, define = yes;
</verb>

in the linker configuration to define the whole 12KB Language Card address
space as memory area for executable code.



<sect>Platform specific header files<p>

Programs containing Apple&nbsp;&rsqb;&lsqb; specific code may use the
<tt/apple2.h/ header file.


<sect1>Apple&nbsp;&rsqb;&lsqb; specific functions<p>

The functions listed below are special for the Apple&nbsp;&rsqb;&lsqb;. See
the <htmlurl url="funcref.html" name="function reference"> for declaration and
usage.

<itemize>
<item>_dos_type
<item>get_ostype
<item>rebootafterexit
</itemize>


<sect1>Hardware access<p>

There's currently no support for direct hardware access. This does not mean
you cannot do it, it just means that there's no help.



<sect>Loadable drivers<p>


<sect1>Graphics drivers<p>

<descrip>

  <tag><tt/a2.lo.tgi/</tag>
  This driver features a resolution of 40&times;48 with 16 colors.

  <tag><tt/a2.hi.tgi/</tag>
  This driver features a resolution of 280&times;192 with 8 colors and two
  hires pages. Note that programs using this driver will have to be linked
  with <tt/--start-addr $4000/ to reserve the first hires page or with
  <tt/--start-addr $6000/ to reserve both hires pages.
  
  In memory constrained situations the memory from &dollar;803 to &dollar;1FFF
  can be made available to a program by executing <tt/_heapadd ((void *) 0x0803, 0x17FD);/
  at the beginning of <tt/main()/. Doing so is beneficial even if the program
  doesn't use the the heap explicitly because loading the driver (and in fact
  already opening the driver file) uses the heap implicitly.

</descrip><p>


<sect1>Extended memory drivers<p>

<descrip>

  <tag><tt/a2.auxmem.emd/</tag>
  Gives access to 47,5 KB RAM (190 pages of 256 bytes each) on an Extended
  80-Column Text Card.
  
  Note that this driver doesn't check for the actual existence of the memory
  and that it doesn't check for ProDOS 8 RAM disk content!

</descrip><p>


<sect1>Joystick drivers<p>

<descrip>

  <tag><tt/a2.stdjoy.joy/</tag>
  Supports up to two standard analog joysticks connected to the game port of
  the Apple&nbsp;&rsqb;&lsqb;.

</descrip><p>


<sect1>Mouse drivers<p>

<descrip>

  <tag><tt/a2.stdmou.mou/</tag>
  Driver for the AppleMouse&nbsp;II Card. Searches all Apple&nbsp;II slots
  for an AppleMouse&nbsp;II Card compatible firmware. The default bounding
  box is &lsqb;0..279,0..191&rsqb;.
  
  Programs using this driver will have to be linked with <tt/--start-addr $4000/
  to reserve the first hires page if they are intended to run on an
  Apple&nbsp;&rsqb;&lsqb; (in contrast to an Apple&nbsp;//e) because the
  AppleMouse&nbsp;II Card firmware writes to the hires page when initializing
  on that machine.

  Note that the Apple&nbsp;&rsqb;&lsqb; default mouse callbacks support text
  mode only.

</descrip><p>


<sect1>RS232 device drivers<p>

<descrip>

  <tag><tt/a2.ssc.ser/</tag>
  Driver for the Apple&nbsp;II Super Serial Card. Supports up to 19200 baud,
  hardware flow control (RTS/CTS) and interrupt driven receives. Note
  that because of the peculiarities of the 6551 chip transmits are not
  interrupt driven, and the transceiver blocks if the receiver asserts
  flow control because of a full buffer.

  The driver defaults to slot 2. Call <tt/ser_ioctl(0, &lt;slot&gt;)/ prior to
  <tt/ser_open()/ in order to select a different slot. <tt/ser_ioctl()/
  succeeds for all Apple&nbsp;II slots, but <tt/ser_open()/ fails with
  <tt/SER_ERR_NO_DEVICE/ if there's no SSC firmware found in the selected slot.

</descrip><p>



<sect>Limitations<p>


<sect1>DOS 3.3<p>

Although the standard binaries generated by the linker for the Apple&nbsp;&rsqb;&lsqb;
generally run both on DOS 3.3 (with Applesoft BASIC) and on ProDOS 8 (with
BASIC.SYSTEM) there are some limitations for DOS 3.3:

<descrip>

  <tag>Disk File I/O</tag>
  There's no disk file I/O support. Any attempt to use it yields an error with
  <tt/errno/ set to <tt/ENOSYS/. This implicitly means that loadable drivers
  are in general not functional as they depend on disk file I/O. However they
  may be converted to statically linked drivers using the co65 object-file
  converter.

  <tag>Interrupts</tag>
  There's no <tt/interruptor/ support. Any attempt to use it yields the message
  'FAILED TO ALLOC INTERRUPT' on program startup. This implicitly means that
  <tt/a2.stdmou.mou/ and <tt/a2.ssc.ser/ are not functional as they depend on
  interrupts.
  
</descrip><p>


<sect1>DIO<p>

Although <htmlurl url="dio.html" name="DIO"> generally works with all ProDOS 8
devices, the function <htmlurl url="dio-3.html" name="dio_query_sectcount()">
simply always return 280 (which is only correct for a 140KB disk).


<sect1>Direct console I/O<p>

<descrip>

  <tag>Color</tag>
  The Apple&nbsp;&rsqb;&lsqb; has no color text mode. Therefore the functions
  <htmlurl url="funcref-205.html" name="textcolor()">,
  <htmlurl url="funcref-68.html" name="bgcolor()"> and
  <htmlurl url="funcref-69.html" name="bordercolor()"> have no effect.

  <tag>Cursor</tag>
  The Apple&nbsp;&rsqb;&lsqb; has no hardware cursor. Therefore the function
  <htmlurl url="funcref-88.html" name="cursor()"> has no effect.

</descrip><p>



<sect>Other hints<p>


<sect1>Passing arguments to the program<p>

Command line arguments can be passed to <tt/main()/ after BLOAD. Since this is not
supported by BASIC, the following syntax was chosen:

<tscreen><verb>
]CALL2051:REM ARG1 " ARG2 IS QUOTED" ARG3 "" ARG5
</verb></tscreen>

<enum>
<item>Arguments are separated by spaces.
<item>Arguments may be quoted.
<item>Leading and trailing spaces around an argument are ignored. Spaces within
      a quoted argument are allowed.
<item>The first argument passed to <tt/main/ is the program name.
<item>A maximum number of 10 arguments (including the program name) are
      supported.
</enum>


<sect1>Interrupts<p>

The runtime for the Apple&nbsp;&rsqb;&lsqb; uses routines marked as <tt/.CONDES/
type <tt/interruptor/ for ProDOS 8 interrupt handlers. Such routines must be
written as simple machine language subroutines and will be called automatically
by the interrupt handler code when they are linked into a program. See the
discussion of the <tt/.CONDES/ feature in the <htmlurl url="ca65.html"
name="assembler manual">.


<sect1>DIO<p>

The function <htmlurl url="dio-1.html" name="dio_open()"> has the single parameter
<tt/drive_id/ to identify the drive to be opened. Therefore an Apple&nbsp;II
slot and drive pair is mapped to that <tt/drive_id/ according to the formula

<verb>
    drive_id = (slot * 2) + (drive - 1)
</verb>

so that for example slot 6 drive 1 is mapped to <tt/drive_id/ 12.

The function <htmlurl url="dio-1.html" name="dio_open()"> succeeds only if a
formatted disk is present in the drive. However intentionally no check is
performed on the presence of a ProDOS 8 disk. Therefore access to all standard
16-sector disks (as for instance DOS 3.3) is possible.



<sect>Bugs/Feedback<p>

If you have problems using the library, if you find any bugs, or if you're
doing something interesting with it, I would be glad to hear from you. Feel
free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
name="uz@cc65.org">).



<sect>License<p>

This software is provided 'as-is', without any expressed or implied
warranty. In no event will the authors be held liable for any damages
arising from the use of this software.

Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:

<enum>
<item>	The origin of this software must not be misrepresented; you must not
	claim that you wrote the original software. If you use this software
	in a product, an acknowledgment in the product documentation would be
	appreciated but is not required.
<item>	Altered source versions must be plainly marked as such, and must not
	be misrepresented as being the original software.
<item>	This notice may not be removed or altered from any source
	distribution.
</enum>

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