1 <!doctype linuxdoc system>
5 <title>Apple ][ specific information for cc65
6 <author><url url="mailto:ol.sc@web.de" name="Oliver Schmidt">
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 <url 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="https://applecommander.github.io/">) 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 <ref id="apple-sys-cfg" 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 LC/ or per function by enclosing in <tt/#pragma code-name
79 (push, "LC")/ and <tt/#pragma code-name (pop)/. In either case the cc65 runtime
80 system takes care of actually moving the code into the Language Card.
82 The amount of memory available in the Language Card for generated code depends
83 on the <ref id="link-configs" name="linker configuration"> parameters. There are
84 several usefull settings:
88 <tag>LC address: $D400, LC size: $C00</tag>
89 For plain vanilla ProDOS 8 which doesn't actually use the Language Card bank 2
90 memory from $D400 to $DFFF. This is the default setting.
92 <tag>LC address: $D000, LC size: $1000</tag>
93 For ProDOS 8 together with the function <tt/rebootafterexit()/. If a program
94 doesn't quit to the ProDOS 8 dispatcher but rather reboots the machine after
95 exit then a plain vanilla ProDOS 8 doesn't make use of the Language Card bank
98 <tag>LC address: $D000, LC size: $3000</tag>
99 For plain vanilla DOS 3.3 which doesn't make use of the Language Card at all.
105 <sect>Linker configurations<label id="link-configs"><p>
107 The ld65 linker comes with a default config file for the Apple ][,
108 which is used via <tt/-t apple2/.
109 The apple2 package comes with additional secondary linker config files, which
110 are used via <tt/-t apple2 -C <configfile>/.
113 <sect1>default config file (<tt/apple2.cfg/)<label id="apple-def-cfg"><p>
115 Default configuration for a binary program.
121 <tag><tt/STARTADDRESS:/ Program start address</tag>
122 Default: $803. Use <tt/-S <addr>/ to set a different start address.
124 <tag><tt/__EXEHDR__:/ Executable file header</tag>
125 Default: DOS 3.3 header (address and length). Use <tt/-D __EXEHDR__=0/ to omit
128 <tag><tt/__STACKSIZE__:/ C runtime stack size</tag>
129 Default: $800. Use <tt/-D __STACKSIZE__=<size>/ to set a different
132 <tag><tt/__HIMEM__:/ Highest usable memory address presumed at link time</tag>
133 Default: $9600. Use <tt/-D __HIMEM__=<addr>/ to set a different
134 highest usable address.
136 <tag><tt/__LCADDR__:/ Address of code in the Language Card</tag>
137 Default: $D400. Use <tt/-D __LCADDR__=<addr>/ to set a different
140 <tag><tt/__LCSIZE__:/ Size of code in the Language Card</tag>
141 Default: $C00. Use <tt/-D __LCSIZE__=<size>/ to set a different
147 <sect1><tt/apple2-system.cfg/<label id="apple-sys-cfg"><p>
149 Configuration for a system program running on ProDOS 8 and using the memory from
150 $2000 to $BEFF.
156 <tag><tt/__STACKSIZE__:/ C runtime stack size</tag>
157 Default: $800. Use <tt/-D __STACKSIZE__=<size>/ to set a different
160 <tag><tt/__LCADDR__:/ Address of code in the Language Card</tag>
161 Default: $D400. Use <tt/-D __LCADDR__=<addr>/ to set a different
164 <tag><tt/__LCSIZE__:/ Size of code in the Language Card</tag>
165 Default: $C00. Use <tt/-D __LCSIZE__=<size>/ to set a different
171 <sect1><tt/apple2-hgr.cfg/<p>
173 Configuration for a program including a hires page. See <tt>testcode/lib/apple/hgrtest.c</tt>
174 for an example of such a program.
180 <tag><tt/STARTADDRESS:/ Program start address</tag>
181 Default: $803. Use <tt/-S <addr>/ to set a different start address.
183 <tag><tt/__EXEHDR__:/ Executable file header</tag>
184 Default: DOS 3.3 header (address and length). Use <tt/-D __EXEHDR__=0/ to omit
187 <tag><tt/__STACKSIZE__:/ C runtime stack size</tag>
188 Default: $800. Use <tt/-D __STACKSIZE__=<size>/ to set a different
191 <tag><tt/__HIMEM__:/ Highest usable memory address presumed at link time</tag>
192 Default: $9600. Use <tt/-D __HIMEM__=<addr>/ to set a different
193 highest usable address.
195 <tag><tt/__LCADDR__:/ Address of code in the Language Card</tag>
196 Default: $D400. Use <tt/-D __LCADDR__=<addr>/ to set a different
199 <tag><tt/__LCSIZE__:/ Size of code in the Language Card</tag>
200 Default: $C00. Use <tt/-D __LCSIZE__=<size>/ to set a different
206 <sect1><tt/apple2-overlay.cfg/<p>
208 Configuration for an overlay program with up to nine overlays. The overlay files
209 don't include the DOS 3.3 header. See <tt>samples/overlaydemo.c</tt> for more
210 information on overlays.
216 <tag><tt/STARTADDRESS:/ Program start address</tag>
217 Default: $803. Use <tt/-S <addr>/ to set a different start address.
219 <tag><tt/__EXEHDR__:/ Executable file header</tag>
220 Default: DOS 3.3 header (address and length). Use <tt/-D __EXEHDR__=0/ to omit
223 <tag><tt/__STACKSIZE__:/ C runtime stack size</tag>
224 Default: $800. Use <tt/-D __STACKSIZE__=<size>/ to set a different
227 <tag><tt/__HIMEM__:/ Highest usable memory address presumed at link time</tag>
228 Default: $9600. Use <tt/-D __HIMEM__=<addr>/ to set a different
229 highest usable address.
231 <tag><tt/__LCADDR__:/ Address of code in the Language Card</tag>
232 Default: $D400. Use <tt/-D __LCADDR__=<addr>/ to set a different
235 <tag><tt/__LCSIZE__:/ Size of code in the Language Card</tag>
236 Default: $C00. Use <tt/-D __LCSIZE__=<size>/ to set a different
239 <tag><tt/__OVERLAYSIZE__:/ Size of code in the overlays</tag>
240 Default: $1000. Use <tt/-D __OVERLAYSIZE__=<size>/ to set a different
246 <sect1><tt/apple2-asm.cfg/<p>
248 Configuration for an assembler program that doesn't need a special setup.
254 <tag><tt/STARTADDRESS:/ Program start address</tag>
255 Default: $803. Use <tt/-S <addr>/ to set a different start address.
257 <tag><tt/__EXEHDR__:/ Executable file header</tag>
258 Default: No header. Use <tt/-u __EXEHDR__ apple2.lib/ to add a DOS 3.3 header
259 (address and length).
265 <sect>ProDOS 8 system programs<p>
267 ProDOS 8 system programs are always loaded to the start address $2000.
268 For cc65 programs this means that the 6 KB from $800 to $2000 are
269 by default unused. There are however several options to make use of that memory
273 <sect1>LOADER.SYSTEM<p>
275 The easiest (and for really large programs in fact the only) way to have a cc65
276 program use the memory from $800 to $2000 is to link it as binary
277 (as opposed to system) program using the default linker configuration
278 <ref id="apple-def-cfg" name="apple2.cfg"> with <tt/__HIMEM__/ set to $BF00
279 and load it with the LOADER.SYSTEM utility. The program then works like a system
280 program (i.e. quits to the ProDOS dispatcher).
282 Using LOADER.SYSTEM is as simple as copying it to the ProDOS 8 directory of the
283 program to load under name <program>.SYSTEM as a system program. For
284 example the program <tt/MYPROG/ is loaded by <tt/MYPROG.SYSTEM/.
289 If the cc65 program can be successfully linked as system program using the linker
290 configuration <ref id="apple-sys-cfg" name="apple2-system.cfg">, but
291 uses the heap either explicitly or implicitly (i.e. by loading a driver) then
292 the memory from $800 to $2000 can be added to the heap by calling
293 <tt/_heapadd ((void *) 0x0800, 0x1800);/ at the beginning of <tt/main()/.
296 <sect1>ProDOS 8 I/O buffers<p>
298 ProDOS 8 requires for every open file a page-aligned 1 KB I/O buffer. By default
299 these buffers are allocated by the cc65 runtime system on the heap using
300 <tt/posix_memalign()/. While this is generally the best solution it means quite
301 some overhead for (especially rather small) cc65 programs which do open files
302 but don't make use of the heap otherwise.
304 The apple2 package comes with the alternative ProDOS 8 I/O buffer allocation
305 module <tt/apple2-iobuf-0800.o/ which uses the memory between $800 and
306 the program start address for the 1 KB I/O buffers. For system programs (with
307 start address $2000) this results in up to 6 I/O buffers and thus up to 6
308 concurrently open files.
310 While using <tt/_heapadd()/ as described in the section above together with the
311 default I/O buffer allocation basically yields the same placement of I/O buffers
312 in memory the primary benefit of <tt/apple2-iobuf-0800.o/ is a reduction in code
313 size - and thus program file size - of more than 1400 bytes.
315 Using <tt/apple2-iobuf-0800.o/ is as simple as placing it on the linker command
319 cl65 -t apple2 -C apple2-system.cfg myprog.c apple2-iobuf-0800.o
324 <sect>Platform specific header files<p>
326 Programs containing Apple ][ specific code may use the
327 <tt/apple2.h/ header file.
330 <sect1>Apple ][ specific functions<p>
332 The functions listed below are special for the Apple ][. See
333 the <url url="funcref.html" name="function reference"> for declaration and
341 <item>rebootafterexit
342 <item>ser_apple2_slot
347 <sect1>Hardware access<p>
349 There's currently no support for direct hardware access. This does not mean
350 you cannot do it, it just means that there's no help.
354 <sect>Loadable drivers<p>
356 The names in the parentheses denote the symbols to be used for static linking of the drivers.
359 <sect1>Graphics drivers<p>
363 <tag><tt/a2.lo.tgi (a2_lo_tgi)/</tag>
364 This driver features a resolution of 40×48 with 16 colors.
366 The function <tt/tgi_apple2_mix()/ allows to activate 4 lines of text. The
367 function clears the corresponding area at the bottom of the screen.
369 <tag><tt/a2.hi.tgi (a2_hi_tgi)/</tag>
370 This driver features a resolution of 280×192 with 8 colors and two
371 hires pages. Note that programs using this driver will have to be linked
372 with <tt/-S $4000/ to reserve the first hires page or with <tt/-S $6000/
373 to reserve both hires pages.
375 The function <tt/tgi_apple2_mix()/ allows to activate 4 lines of text. The
376 function doesn't clear the corresponding area at the bottom of the screen.
378 In memory constrained situations the memory from $803 to $1FFF
379 can be made available to a program by calling <tt/_heapadd ((void *) 0x0803, 0x17FD);/
380 at the beginning of <tt/main()/. Doing so is beneficial even if the program
381 doesn't use the the heap explicitly because loading the driver (and in fact
382 already opening the driver file) uses the heap implicitly.
387 <sect1>Extended memory drivers<p>
391 <tag><tt/a2.auxmem.emd (a2_auxmem_emd)/</tag>
392 Gives access to 47.5 KB RAM (190 pages of 256 bytes each) on an Extended
395 Note that this driver doesn't check for the actual existence of the memory
396 and that it doesn't check for ProDOS 8 RAM disk content!
401 <sect1>Joystick drivers<p>
405 <tag><tt/a2.stdjoy.joy (a2_stdjoy_joy)/</tag>
406 Supports up to two standard analog joysticks connected to the game port of
407 the Apple ][.
412 <sect1>Mouse drivers<p>
416 <tag><tt/a2.stdmou.mou (a2_stdmou_mou)/</tag>
417 Driver for the AppleMouse II Card. Searches all Apple II slots
418 for an AppleMouse II Card compatible firmware. The default bounding
419 box is [0..279,0..191].
421 Programs using this driver will have to be linked with <tt/-S $4000/
422 to reserve the first hires page if they are intended to run on an
423 Apple ][ (in contrast to an Apple //e) because the
424 AppleMouse II Card firmware writes to the hires page when initializing
427 Note that the Apple ][ default mouse callbacks support text
433 <sect1>RS232 device drivers<p>
437 <tag><tt/a2.ssc.ser (a2_ssc_ser)/</tag>
438 Driver for the Apple II Super Serial Card. Supports up to 19200 baud,
439 hardware flow control (RTS/CTS) and interrupt driven receives. Note
440 that because of the peculiarities of the 6551 chip transmits are not
441 interrupt driven, and the transceiver blocks if the receiver asserts
442 flow control because of a full buffer.
444 The driver defaults to slot 2. Call <tt/ser_apple2_slot()/ prior to
445 <tt/ser_open()/ in order to select a different slot. <tt/ser_apple2_slot()/
446 succeeds for all Apple II slots, but <tt/ser_open()/ fails with
447 <tt/SER_ERR_NO_DEVICE/ if there's no SSC firmware found in the selected slot.
458 Although the standard binaries generated by the linker for the Apple ][
459 generally run both on DOS 3.3 (with Applesoft BASIC) and on ProDOS 8 (with
460 BASIC.SYSTEM) there are some limitations for DOS 3.3:
464 <tag>Disk File I/O</tag>
465 There's no disk file I/O support. Any attempt to use it yields an error with
466 <tt/errno/ set to <tt/ENOSYS/. This implicitly means that loadable drivers
467 are in general not functional as they depend on disk file I/O. Therefore the statically
468 linked drivers have to be used instead.
471 There's no <tt/interruptor/ support. Any attempt to use it yields the message
472 'FAILED TO ALLOC INTERRUPT' on program startup. This implicitly means that
473 mouse and RS232 device drivers are not functional as they depend on interrupts.
478 <sect1>Direct console I/O<p>
483 The Apple ][ has no color text mode. Therefore the functions textcolor(),
484 bgcolor() and bordercolor() have no effect.
493 <sect1>Passing arguments to the program<p>
495 Command line arguments can be passed to <tt/main()/ after BLOAD. Since this is not
496 supported by BASIC, the following syntax was chosen:
499 ]CALL2051:REM ARG1 " ARG2 IS QUOTED" ARG3 "" ARG5
503 <item>Arguments are separated by spaces.
504 <item>Arguments may be quoted.
505 <item>Leading and trailing spaces around an argument are ignored. Spaces within
506 a quoted argument are allowed.
507 <item>The first argument passed to <tt/main/ is the program name.
508 <item>A maximum number of 10 arguments (including the program name) are
515 The runtime for the Apple ][ uses routines marked as
516 <tt/.INTERRUPTOR/ for ProDOS 8 interrupt handlers. Such routines must be
517 written as simple machine language subroutines and will be called
518 automatically by the interrupt handler code when they are linked into a
519 program. See the discussion of the <tt/.CONDES/ feature in the <url
520 url="ca65.html" name="assembler manual">.
528 The function <url url="dio.html#s1" name="dio_open()"> has the single
529 parameter <tt/device/ to identify the device to be opened. Therefore an
530 Apple II slot and drive pair is mapped to that <tt/device/ according
534 device = slot + (drive - 1) * 8
537 so that for example slot 6 drive 2 is mapped to <tt/device/ 14.
540 The function <url url="dio.html#s3" name="dio_query_sectcount()"> returns
541 the correct sector count for all ProDOS 8 disks. However for any non-ProDOS 8
542 disk it simply always returns 280 (which is only correct for a 140 KB disk).
543 This condition is indicated by the <tt/_oserror/ value 82.
548 <sect1>Specifying file types for fopen<p>
552 <tag>Explanation of File Types</tag>
554 ProDOS associates a file type and an auxiliary type with each file.
555 These type specifications are separate from the file's name, unlike
556 Windows which uses the file name's suffix (a.k.a.
557 extension) to specify the file type. For example, <tt/.exe/,
558 <tt/.doc/, or <tt/.bat/.
560 Machine-Language Interface (MLI) functions for creating and opening
561 files require these types to be specified. And if they don't match
562 with the file being opened, the operation may fail.
564 In contrast, the ISO C function <tt/fopen()/ and the POSIX function
565 <tt/open()/ have no parameter to specify either a file type or an
566 auxiliary type. Therefore, some additional mechanism for specifying
567 the file types is needed.
569 <tag>Specifying the File Type and Auxiliary Type</tag>
571 There are two global variables provided that allow the file type
572 and auxiliary type to be specified before a call to <tt/fopen()/
573 or <tt/open()/. They are defined in <tt/apple2_filetype.h/:
577 extern unsigned char _filetype; /* Default: PRODOS_T_BIN */
578 extern unsigned int _auxtype; /* Default: 0 */
582 The header file <tt/apple2_filetype.h/ also defines many values
583 that can be used to set these variables. It is included in
584 <tt/apple2.h/, which is in turn included in <tt/apple2enh.h/.
585 So it isn't necessary to include it directly. Just
586 include one of <tt/apple2.h/ or <tt/apple2enh.h/.
590 A text file cannot be created with just the
591 standard C functions because they default to the binary type
592 <tt/PRODOS_T_BIN/. The <tt/_filetype/ variable must be set to
593 <tt/PRODOS_T_TXT/ to create a text file.
596 <tt/_auxtype/ specifies the record length. A zero record
597 length text file is referred to as a sequential text file.
598 This is equivalent to text files on
599 other operating systems, except that the line terminator is a
600 carriage return instead of a line-feed (Linux/BSD/MacOS) or
601 carriage return, line-feed pair (Windows).
603 The "sequential" text file terminology is in contrast to a
604 "random-access" text file which would
605 have a fixed-length, non-zero record length, so that the
606 file position of any individual record can be calculated.
608 For this example, the
609 <tt/_auxtype/ does not need to be set because it defaults to
610 the desired value, which is zero. To be more explicit,
611 <tt/_auxtype/ can also be set to <tt/PRODOS_AUX_T_TXT_SEQ/
612 which is defined as zero.
616 #include <stdio.h>
617 #include <string.h>
618 #include <errno.h>
619 #include <apple2.h>
624 char *name = "MY.FAVS";
626 /*-----------------------------*/
628 _filetype = PRODOS_T_TXT;
629 _auxtype = PRODOS_AUX_T_TXT_SEQ;
631 /*-----------------------------*/
633 if ((out = fopen(name, "w")) != NULL) {
634 fputs("Jorah Mormont\r", out);
635 fputs("Brienne of Tarth\r", out);
636 fputs("Daenerys Targaryen\r", out);
637 fputs("Sandor Clegane\r", out);
638 if (fclose(out) == EOF) {
639 fprintf(stderr, "fclose failed for %s: %s", name, strerror(errno));
643 fprintf(stderr, "fopen failed for %s: %s", name, strerror(errno));
654 This software is provided 'as-is', without any expressed or implied
655 warranty. In no event will the authors be held liable for any damages
656 arising from the use of this software.
658 Permission is granted to anyone to use this software for any purpose,
659 including commercial applications, and to alter it and redistribute it
660 freely, subject to the following restrictions:
663 <item> The origin of this software must not be misrepresented; you must not
664 claim that you wrote the original software. If you use this software
665 in a product, an acknowledgment in the product documentation would be
666 appreciated but is not required.
667 <item> Altered source versions must be plainly marked as such, and must not
668 be misrepresented as being the original software.
669 <item> This notice may not be removed or altered from any source