1 <!doctype linuxdoc system>
5 <title>Apple ][ specific information for cc65
6 <author>Oliver Schmidt, <htmlurl url="mailto:ol.sc@web.de" name="ol.sc@web.de">
10 An overview over the Apple ][ runtime system as it is
11 implemented for the cc65 C compiler.
14 <!-- Table of contents -->
17 <!-- Begin the document -->
21 This file contains an overview of the Apple ][ runtime system
22 as it comes with the cc65 C compiler. It describes the memory layout,
23 Apple ][ specific header files, available drivers, and any
24 pitfalls specific to that platform.
26 Please note that Apple ][ specific functions are just mentioned
27 here, they are described in detail in the separate <htmlurl url="funcref.html"
28 name="function reference">. Even functions marked as "platform dependent" may
29 be available on more than one platform. Please see the function reference for
34 <sect>Binary format<p>
36 The standard binary file format generated by the linker for the
37 Apple ][ target is a binary program with a 4 byte DOS 3.3 header
38 containing the load address and load length. The default load address is
41 <bf/AppleCommander 1.3.5/ or later (available at <url
42 url="http://applecommander.sourceforge.net/">) includes the option <tt/-cc65/
43 that allows to put binary files with a DOS 3.3 header onto disk images
44 containing DOS 3.3 as well as ProDOS 8.
46 For ProDOS 8 system programs the load address is fixed to $2000 so there
47 is no need for a header. Thus the linker configuration
48 <htmlurl url="apple2-4.html#ss4.3" name="apple2-system.cfg"> for those programs
49 omits the DOS 3.3 header. The right AppleCommander option to put system files
50 without a header on a ProDOS 8 disk image is <tt/-p/.
53 <sect>Memory layout<p>
55 In the standard setup, cc65 generated programs use the memory from
56 $803 to $95FF, so 35.5 KB of RAM are available.
63 The C runtime stack is located at HIMEM and grows downwards, regardless of
64 how your linker config file is setup.
67 The C heap is located at the end of the program and grows towards the C
72 While running <tt/main()/ the Language Card bank 2 is enabled for read access.
73 However while running module constructors/destructors the Language Card is disabled.
75 Enabling the Language Card allows to use it as additional memory for cc65
76 generated code. However code is never automatically placed there. Rather code
77 needs to be explicitly placed in the Language Card either per file by compiling
78 with <tt/--code-name HIGHCODE/ or per function by enclosing in <tt/#pragma
79 code-name (push, "HIGHCODE")/ and <tt/#pragma code-name (pop)/. In either case the
80 cc65 runtime system takes care of actually moving the code into the Language
83 The amount of memory available in the Language Card for generated code depends
84 on the chosen <htmlurl url="apple2-4.html" name="linker configuration">.
88 <sect>Linker configurations<p>
90 The ld65 linker comes with a builtin config file for the Apple ][,
91 which is used via <tt/-t apple2/ (and displayed via <tt/--dump-config apple2/).
92 The apple2 package comes with additional secondary linker config files, which
93 are used via <tt/-C <configfile>/.
96 <sect1>builtin config file<p>
98 Default configuration optimized for a binary program running on ProDOS 8 with
99 BASIC.SYSTEM. A plain vanilla ProDOS 8 doesn't actually use the Language Card
100 bank 2 memory from $D400 to $DFFF.
104 <tag><tt/RAM:/ Main memory area</tag>
105 From $803 to $95FF (35.5 KB)
107 <tag><tt/LC:/ Language Card memory area</tag>
108 From $D400 to $DFFF (3 KB)
110 <tag><tt/STARTADDRESS:/ Program start address</tag>
111 Variable (default: $803)
113 <tag><tt/HEADER:/ Binary file header</tag>
114 DOS 3.3 header (address and length)
119 <sect1><tt/apple2-dos33.cfg/<p>
121 Configuration optimized for a binary program running on DOS 3.3. A plain
122 vanilla DOS 3.3 doesn't make use of the Language Card at all.
126 <tag><tt/RAM:/ Main memory area</tag>
127 From $803 to $95FF (35.5 KB)
129 <tag><tt/LC:/ Language Card memory area</tag>
130 From $D000 to $FFFF (12 KB)
132 <tag><tt/STARTADDRESS:/ Program start address</tag>
133 Variable (default: $803)
135 <tag><tt/HEADER:/ Binary file header</tag>
136 DOS 3.3 header (address and length)
141 <sect1><tt/apple2-system.cfg/<p>
143 Configuration for a system program running on ProDOS 8.
147 <tag><tt/RAM:/ Main memory area</tag>
148 From $2000 to $BEFF (39.75 KB)
150 <tag><tt/LC:/ Language Card memory area</tag>
151 From $D400 to $DFFF (3 KB)
153 <tag><tt/STARTADDRESS:/ Program start address</tag>
156 <tag><tt/HEADER:/ Binary file header</tag>
162 <sect1><tt/apple2-loader.cfg/<p>
164 Configuration optimized for a binary program running on ProDOS 8 without
165 BASIC.SYSTEM. Intended to be used with <bf/LOADER.SYSTEM - an
166 Apple ][ ProDOS 8 loader for cc65 programs/, which is available
167 in the cc65 User Contributions section.
169 A program loaded by LOADER.SYSTEM works like a ProDOS 8 system program but
170 isn't tied to the start address $2000. Thus with the default start
171 address $800 the main memory area is increased by 6 KB.
175 <tag><tt/RAM:/ Main memory area</tag>
176 From $800 to $BEFF (45.75 KB)
178 <tag><tt/LC:/ Language Card memory area</tag>
179 From $D400 to $DFFF (3 KB)
181 <tag><tt/STARTADDRESS:/ Program start address</tag>
182 Variable (default: $800)
184 <tag><tt/HEADER:/ Binary file header</tag>
185 DOS 3.3 header (address and length)
190 <sect1><tt/apple2-reboot.cfg/<p>
192 Configuration optimized for a binary program running on ProDOS 8 without
193 BASIC.SYSTEM. Intended to be used with <bf/LOADER.SYSTEM - an
194 Apple ][ ProDOS 8 loader for cc65 programs/ (see above) together
195 with the function <tt/rebootafterexit()/.
197 If a ProDOS 8 system program doesn't quit to the ProDOS 8 dispatcher but rather
198 reboots the machine after exit then a plain vanilla ProDOS 8 doesn't make use of
199 the Language Card bank 2 at all.
201 This setup makes nearly 50 KB available to a cc65 program - on a 64 KB machine!
205 <tag><tt/RAM:/ Main memory area</tag>
206 From $800 to $BEFF (45.75 KB)
208 <tag><tt/LC:/ Language Card memory area</tag>
209 From $D000 to $DFFF (4 KB)
211 <tag><tt/STARTADDRESS:/ Program start address</tag>
212 Variable (default: $800)
214 <tag><tt/HEADER:/ Binary file header</tag>
215 DOS 3.3 header (address and length)
221 <sect>ProDOS 8 system programs<p>
223 ProDOS 8 system programs are always loaded to the start address $2000.
224 For cc65 programs this means that the 6 KB from $800 to $2000 are
225 by default unused. There are however several options to make use of that memory
229 <sect1>LOADER.SYSTEM<p>
231 The easiest (and for really large programs in fact the only) way to have a cc65
232 program use the memory from $800 to $2000 is to link it as binary
233 (as opposed to system) program using the linker configuration
234 <htmlurl url="apple2-4.html#ss4.4" name="apple2-loader.cfg"> with start address
235 $800 and load it with <bf/LOADER.SYSTEM - an Apple ][
236 ProDOS 8 loader for cc65 programs/. The program then works like a system program
237 (i.e. quits to the ProDOS dispatcher).
239 Using LOADER.SYSTEM is as simple as copying it to the ProDOS 8 directory of the
240 program to load under name <program>.SYSTEM as a system program. For
241 example the program <tt/MYPROG/ is loaded by <tt/MYPROG.SYSTEM/.
246 If the cc65 program can be successfully linked as system program using the linker
247 configuration <htmlurl url="apple2-4.html#ss4.3" name="apple2-system.cfg"> but
248 uses the heap either explicitly or implicitly (i.e. by loading a driver) then
249 the memory from $800 to $2000 can be added to the heap by calling
250 <tt/_heapadd ((void *) 0x0800, 0x1800);/ at the beginning of <tt/main()/.
253 <sect1>ProDOS 8 I/O buffers<p>
255 ProDOS 8 requires for every open file a page-aligned 1 KB I/O buffer. By default
256 these buffers are allocated by the cc65 runtime system on the heap using
257 <tt/posix_memalign()/. While this is generally the best solution it means quite
258 some overhead for (especially rather small) cc65 programs which do open files
259 but don't make use of the heap otherwise.
261 The apple2 package comes with the alternative ProDOS 8 I/O buffer allocation
262 module <tt/apple2-iobuf-0800.o/ which uses the memory between $800 and
263 the program start address for the 1 KB I/O buffers. For system programs (with
264 start address $2000) this results in up to 6 I/O buffers and thus up to 6
265 concurrently open files.
267 While using <tt/_heapadd()/ as described in the section above together with the
268 default I/O buffer allocation basically yields the same placement of I/O buffers
269 in memory the primary benefit of <tt/apple2-iobuf-0800.o/ is a reduction in code
270 size - and thus program file size - of more than 1400 bytes.
272 Using <tt/apple2-iobuf-0800.o/ is as simple as placing it on the linker command
276 cl65 -t apple2 -C apple2-system.cfg myprog.c apple2-iobuf-0800.o
281 <sect>Platform specific header files<p>
283 Programs containing Apple ][ specific code may use the
284 <tt/apple2.h/ header file.
287 <sect1>Apple ][ specific functions<p>
289 The functions listed below are special for the Apple ][. See
290 the <htmlurl url="funcref.html" name="function reference"> for declaration and
298 <item>rebootafterexit
299 <item>ser_apple2_slot
304 <sect1>Hardware access<p>
306 There's currently no support for direct hardware access. This does not mean
307 you cannot do it, it just means that there's no help.
311 <sect>Loadable drivers<p>
314 <sect1>Graphics drivers<p>
318 <tag><tt/a2.lo.tgi/</tag>
319 This driver features a resolution of 40×48 with 16 colors.
321 The function <tt/tgi_apple2_mix()/ allows to activate 4 lines of text. The
322 function clears the corresponding area at the bottom of the screen.
324 <tag><tt/a2.hi.tgi/</tag>
325 This driver features a resolution of 280×192 with 8 colors and two
326 hires pages. Note that programs using this driver will have to be linked
327 with <tt/--start-addr $4000/ to reserve the first hires page or with
328 <tt/--start-addr $6000/ to reserve both hires pages.
330 The function <tt/tgi_apple2_mix()/ allows to activate 4 lines of text. The
331 function doesn't clear the corresponding area at the bottom of the screen.
333 In memory constrained situations the memory from $803 to $1FFF
334 can be made available to a program by calling <tt/_heapadd ((void *) 0x0803, 0x17FD);/
335 at the beginning of <tt/main()/. Doing so is beneficial even if the program
336 doesn't use the the heap explicitly because loading the driver (and in fact
337 already opening the driver file) uses the heap implicitly.
342 <sect1>Extended memory drivers<p>
346 <tag><tt/a2.auxmem.emd/</tag>
347 Gives access to 47.5 KB RAM (190 pages of 256 bytes each) on an Extended
350 Note that this driver doesn't check for the actual existence of the memory
351 and that it doesn't check for ProDOS 8 RAM disk content!
356 <sect1>Joystick drivers<p>
360 <tag><tt/a2.stdjoy.joy/</tag>
361 Supports up to two standard analog joysticks connected to the game port of
362 the Apple ][.
367 <sect1>Mouse drivers<p>
371 <tag><tt/a2.stdmou.mou/</tag>
372 Driver for the AppleMouse II Card. Searches all Apple II slots
373 for an AppleMouse II Card compatible firmware. The default bounding
374 box is [0..279,0..191].
376 Programs using this driver will have to be linked with <tt/--start-addr $4000/
377 to reserve the first hires page if they are intended to run on an
378 Apple ][ (in contrast to an Apple //e) because the
379 AppleMouse II Card firmware writes to the hires page when initializing
382 Note that the Apple ][ default mouse callbacks support text
388 <sect1>RS232 device drivers<p>
392 <tag><tt/a2.ssc.ser/</tag>
393 Driver for the Apple II Super Serial Card. Supports up to 19200 baud,
394 hardware flow control (RTS/CTS) and interrupt driven receives. Note
395 that because of the peculiarities of the 6551 chip transmits are not
396 interrupt driven, and the transceiver blocks if the receiver asserts
397 flow control because of a full buffer.
399 The driver defaults to slot 2. Call <tt/ser_apple2_slot()/ prior to
400 <tt/ser_open()/ in order to select a different slot. <tt/ser_apple2_slot()/
401 succeeds for all Apple II slots, but <tt/ser_open()/ fails with
402 <tt/SER_ERR_NO_DEVICE/ if there's no SSC firmware found in the selected slot.
413 Although the standard binaries generated by the linker for the Apple ][
414 generally run both on DOS 3.3 (with Applesoft BASIC) and on ProDOS 8 (with
415 BASIC.SYSTEM) there are some limitations for DOS 3.3:
419 <tag>Disk File I/O</tag>
420 There's no disk file I/O support. Any attempt to use it yields an error with
421 <tt/errno/ set to <tt/ENOSYS/. This implicitly means that loadable drivers
422 are in general not functional as they depend on disk file I/O. However they
423 may be converted to statically linked drivers using the co65 object-file
427 There's no <tt/interruptor/ support. Any attempt to use it yields the message
428 'FAILED TO ALLOC INTERRUPT' on program startup. This implicitly means that
429 <tt/a2.stdmou.mou/ and <tt/a2.ssc.ser/ are not functional as they depend on
435 <sect1>Direct console I/O<p>
440 The Apple ][ has no color text mode. Therefore the functions
441 <htmlurl url="funcref-205.html" name="textcolor()">,
442 <htmlurl url="funcref-68.html" name="bgcolor()"> and
443 <htmlurl url="funcref-69.html" name="bordercolor()"> have no effect.
446 The Apple ][ has no hardware cursor. Therefore the function
447 <htmlurl url="funcref-88.html" name="cursor()"> has no effect.
456 <sect1>Passing arguments to the program<p>
458 Command line arguments can be passed to <tt/main()/ after BLOAD. Since this is not
459 supported by BASIC, the following syntax was chosen:
462 ]CALL2051:REM ARG1 " ARG2 IS QUOTED" ARG3 "" ARG5
466 <item>Arguments are separated by spaces.
467 <item>Arguments may be quoted.
468 <item>Leading and trailing spaces around an argument are ignored. Spaces within
469 a quoted argument are allowed.
470 <item>The first argument passed to <tt/main/ is the program name.
471 <item>A maximum number of 10 arguments (including the program name) are
478 The runtime for the Apple ][ uses routines marked as
479 <tt/.INTERRUPTOR/ for ProDOS 8 interrupt handlers. Such routines must be
480 written as simple machine language subroutines and will be called
481 automatically by the interrupt handler code when they are linked into a
482 program. See the discussion of the <tt/.CONDES/ feature in the <htmlurl
483 url="ca65.html" name="assembler manual">.
491 The function <htmlurl url="dio-1.html" name="dio_open()"> has the single
492 parameter <tt/device/ to identify the device to be opened. Therefore an
493 Apple II slot and drive pair is mapped to that <tt/device/ according
497 device = slot + (drive - 1) * 8
500 so that for example slot 6 drive 2 is mapped to <tt/device/ 14.
503 The function <htmlurl url="dio-3.html" name="dio_query_sectcount()"> returns
504 the correct sector count for all ProDOS 8 disks. However for any non-ProDOS 8
505 disk it simply always returns 280 (which is only correct for a 140 KB disk).
506 This condition is indicated by the <tt/_oserror/ value 82.
512 <sect>Bugs/Feedback<p>
514 If you have problems using the library, if you find any bugs, or if you're
515 doing something interesting with it, I would be glad to hear from you. Feel
516 free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
517 name="uz@cc65.org">).
523 This software is provided 'as-is', without any expressed or implied
524 warranty. In no event will the authors be held liable for any damages
525 arising from the use of this software.
527 Permission is granted to anyone to use this software for any purpose,
528 including commercial applications, and to alter it and redistribute it
529 freely, subject to the following restrictions:
532 <item> The origin of this software must not be misrepresented; you must not
533 claim that you wrote the original software. If you use this software
534 in a product, an acknowledgment in the product documentation would be
535 appreciated but is not required.
536 <item> Altered source versions must be plainly marked as such, and must not
537 be misrepresented as being the original software.
538 <item> This notice may not be removed or altered from any source