1 <!doctype linuxdoc system>
4 <title>Apple ][ specific information for cc65
5 <author><url url="mailto:ol.sc@web.de" name="Oliver Schmidt">
8 An overview over the Apple ][ runtime system as it is
9 implemented for the cc65 C compiler.
12 <!-- Table of contents -->
15 <!-- Begin the document -->
19 This file contains an overview of the Apple ][ runtime system
20 as it comes with the cc65 C compiler. It describes the memory layout,
21 Apple ][ specific header files, available drivers, and any
22 pitfalls specific to that platform.
24 Please note that Apple ][ specific functions are just mentioned
25 here, they are described in detail in the separate <url url="funcref.html"
26 name="function reference">. Even functions marked as "platform dependent" may
27 be available on more than one platform. Please see the function reference for
32 <sect>Binary format<p>
34 The standard binary file format generated by the linker for the
35 Apple ][ target is an <url name="AppleSingle"
36 url="http://kaiser-edv.de/documents/AppleSingle_AppleDouble.pdf"> file.
37 The default load address is $803.
39 <bf/AppleCommander 1.4.0/ or later (available at <url
40 url="https://applecommander.github.io/">) includes the option <tt/-as/ that
41 allows to put AppleSingle files onto disk images containing DOS 3.3 as well
45 <sect>Memory layout<p>
47 In the standard setup, cc65 generated programs use the memory from
48 $803 to $95FF, so 35.5 KB of RAM are available.
55 The C runtime stack is located at HIMEM and grows downwards, regardless of
56 how your linker config file is setup.
59 The C heap is located at the end of the program and grows towards the C
64 While running <tt/main()/ the Language Card bank 2 is enabled for read access.
65 However while running module constructors/destructors the Language Card is disabled.
67 Enabling the Language Card allows to use it as additional memory for cc65
68 generated code. However code is never automatically placed there. Rather code
69 needs to be explicitly placed in the Language Card either per file by compiling
70 with <tt/--code-name LC/ or per function by enclosing in <tt/#pragma code-name
71 (push, "LC")/ and <tt/#pragma code-name (pop)/. In either case the cc65 runtime
72 system takes care of actually moving the code into the Language Card.
74 The amount of memory available in the Language Card for generated code depends
75 on the <ref id="link-configs" name="linker configuration"> parameters. There are
76 several usefull settings:
80 <tag>LC address: $D400, LC size: $C00</tag>
81 For plain vanilla ProDOS 8 which doesn't actually use the Language Card bank 2
82 memory from $D400 to $DFFF. This is the default setting.
84 <tag>LC address: $D000, LC size: $1000</tag>
85 For ProDOS 8 together with the function <tt/rebootafterexit()/. If a program
86 doesn't quit to the ProDOS 8 dispatcher but rather reboots the machine after
87 exit then a plain vanilla ProDOS 8 doesn't make use of the Language Card bank
90 <tag>LC address: $D000, LC size: $3000</tag>
91 For plain vanilla DOS 3.3 which doesn't make use of the Language Card at all.
97 <sect>Linker configurations<label id="link-configs"><p>
99 The ld65 linker comes with a default config file for the Apple ][,
100 which is used via <tt/-t apple2/.
101 The apple2 package comes with additional secondary linker config files, which
102 are used via <tt/-t apple2 -C <configfile>/.
105 <sect1>default config file (<tt/apple2.cfg/)<label id="apple-def-cfg"><p>
107 Default configuration for a binary program.
113 <tag><tt/STARTADDRESS:/ Program start address</tag>
114 Default: $803. Use <tt/-S <addr>/ to set a different start address.
116 <tag><tt/__EXEHDR__:/ AppleSingle executable file header</tag>
117 Default: Yes. Use <tt/-D __EXEHDR__=0/ to omit the AppleSingle header.
119 <tag><tt/__STACKSIZE__:/ C runtime stack size</tag>
120 Default: $800. Use <tt/-D __STACKSIZE__=<size>/ to set a different
123 <tag><tt/__HIMEM__:/ Highest usable memory address presumed at link time</tag>
124 Default: $9600. Use <tt/-D __HIMEM__=<addr>/ to set a different
125 highest usable address.
127 <tag><tt/__LCADDR__:/ Address of code in the Language Card</tag>
128 Default: $D400. Use <tt/-D __LCADDR__=<addr>/ to set a different
131 <tag><tt/__LCSIZE__:/ Size of code in the Language Card</tag>
132 Default: $C00. Use <tt/-D __LCSIZE__=<size>/ to set a different
138 <sect1><tt/apple2-system.cfg/<label id="apple-sys-cfg"><p>
140 Configuration for a system program running on ProDOS 8 and using the memory from
141 $2000 to $BEFF.
147 <tag><tt/__EXEHDR__:/ AppleSingle executable file header</tag>
148 Default: Yes. Use <tt/-D __EXEHDR__=0/ to omit the AppleSingle header.
150 <tag><tt/__STACKSIZE__:/ C runtime stack size</tag>
151 Default: $800. Use <tt/-D __STACKSIZE__=<size>/ to set a different
154 <tag><tt/__LCADDR__:/ Address of code in the Language Card</tag>
155 Default: $D400. Use <tt/-D __LCADDR__=<addr>/ to set a different
158 <tag><tt/__LCSIZE__:/ Size of code in the Language Card</tag>
159 Default: $C00. Use <tt/-D __LCSIZE__=<size>/ to set a different
165 <sect1><tt/apple2-hgr.cfg/<p>
167 Configuration for a program including a hires page. See <tt>testcode/lib/apple/hgrtest.c</tt>
168 for an example of such a program.
174 <tag><tt/STARTADDRESS:/ Program start address</tag>
175 Default: $803. Use <tt/-S <addr>/ to set a different start address.
177 <tag><tt/__EXEHDR__:/ AppleSingle executable file header</tag>
178 Default: Yes. Use <tt/-D __EXEHDR__=0/ to omit the AppleSingle header.
180 <tag><tt/__STACKSIZE__:/ C runtime stack size</tag>
181 Default: $800. Use <tt/-D __STACKSIZE__=<size>/ to set a different
184 <tag><tt/__HIMEM__:/ Highest usable memory address presumed at link time</tag>
185 Default: $9600. Use <tt/-D __HIMEM__=<addr>/ to set a different
186 highest usable address.
188 <tag><tt/__LCADDR__:/ Address of code in the Language Card</tag>
189 Default: $D400. Use <tt/-D __LCADDR__=<addr>/ to set a different
192 <tag><tt/__LCSIZE__:/ Size of code in the Language Card</tag>
193 Default: $C00. Use <tt/-D __LCSIZE__=<size>/ to set a different
199 <sect1><tt/apple2-overlay.cfg/<p>
201 Configuration for an overlay program with up to nine overlays. The overlay files
202 don't include the AppleSingle header. See <tt>samples/overlaydemo.c</tt> for more
203 information on overlays.
209 <tag><tt/STARTADDRESS:/ Program start address</tag>
210 Default: $803. Use <tt/-S <addr>/ to set a different start address.
212 <tag><tt/__EXEHDR__:/ AppleSingle executable file header</tag>
213 Default: Yes. Use <tt/-D __EXEHDR__=0/ to omit the AppleSingle header.
215 <tag><tt/__STACKSIZE__:/ C runtime stack size</tag>
216 Default: $800. Use <tt/-D __STACKSIZE__=<size>/ to set a different
219 <tag><tt/__HIMEM__:/ Highest usable memory address presumed at link time</tag>
220 Default: $9600. Use <tt/-D __HIMEM__=<addr>/ to set a different
221 highest usable address.
223 <tag><tt/__LCADDR__:/ Address of code in the Language Card</tag>
224 Default: $D400. Use <tt/-D __LCADDR__=<addr>/ to set a different
227 <tag><tt/__LCSIZE__:/ Size of code in the Language Card</tag>
228 Default: $C00. Use <tt/-D __LCSIZE__=<size>/ to set a different
231 <tag><tt/__OVERLAYSIZE__:/ Size of code in the overlays</tag>
232 Default: $1000. Use <tt/-D __OVERLAYSIZE__=<size>/ to set a different
238 <sect1><tt/apple2-asm.cfg/<p>
240 Configuration for an assembler program that doesn't need a special setup.
246 <tag><tt/STARTADDRESS:/ Program start address</tag>
247 Default: $803. Use <tt/-S <addr>/ to set a different start address.
249 <tag><tt/__EXEHDR__:/ AppleSingle executable file header</tag>
250 Default: No. Use <tt/-u __EXEHDR__ apple2.lib/ to add the AppleSingle header.
256 <sect>ProDOS 8 system programs<p>
258 ProDOS 8 system programs are always loaded to the start address $2000.
259 For cc65 programs this means that the 6 KB from $800 to $2000 are
260 by default unused. There are however several options to make use of that memory
264 <sect1>LOADER.SYSTEM<p>
266 The easiest (and for really large programs in fact the only) way to have a cc65
267 program use the memory from $800 to $2000 is to link it as binary
268 (as opposed to system) program using the default linker configuration
269 <ref id="apple-def-cfg" name="apple2.cfg"> with <tt/__HIMEM__/ set to $BF00
270 and load it with the LOADER.SYSTEM utility. The program then works like a system
271 program (i.e. quits to the ProDOS dispatcher).
273 Using LOADER.SYSTEM is as simple as copying it to the ProDOS 8 directory of the
274 program to load under name <program>.SYSTEM as a system program. For
275 example the program <tt/MYPROG/ is loaded by <tt/MYPROG.SYSTEM/. The right
276 AppleCommander option to put LOADER.SYSTEM on a ProDOS 8 disk image is <tt/-p/.
281 If the cc65 program can be successfully linked as system program using the linker
282 configuration <ref id="apple-sys-cfg" name="apple2-system.cfg">, but
283 uses the heap either explicitly or implicitly (i.e. by loading a driver) then
284 the memory from $800 to $2000 can be added to the heap by calling
285 <tt/_heapadd ((void *) 0x0800, 0x1800);/ at the beginning of <tt/main()/.
288 <sect1>ProDOS 8 I/O buffers<p>
290 ProDOS 8 requires for every open file a page-aligned 1 KB I/O buffer. By default
291 these buffers are allocated by the cc65 runtime system on the heap using
292 <tt/posix_memalign()/. While this is generally the best solution it means quite
293 some overhead for (especially rather small) cc65 programs which do open files
294 but don't make use of the heap otherwise.
296 The apple2 package comes with the alternative ProDOS 8 I/O buffer allocation
297 module <tt/apple2-iobuf-0800.o/ which uses the memory between $800 and
298 the program start address for the 1 KB I/O buffers. For system programs (with
299 start address $2000) this results in up to 6 I/O buffers and thus up to 6
300 concurrently open files.
302 While using <tt/_heapadd()/ as described in the section above together with the
303 default I/O buffer allocation basically yields the same placement of I/O buffers
304 in memory the primary benefit of <tt/apple2-iobuf-0800.o/ is a reduction in code
305 size - and thus program file size - of more than 1400 bytes.
307 Using <tt/apple2-iobuf-0800.o/ is as simple as placing it on the linker command
311 cl65 -t apple2 -C apple2-system.cfg myprog.c apple2-iobuf-0800.o
316 <sect>Platform specific header files<p>
318 Programs containing Apple ][ specific code may use the
319 <tt/apple2.h/ header file.
322 <sect1>Apple ][ specific functions<p>
324 The functions listed below are special for the Apple ][. See
325 the <url url="funcref.html" name="function reference"> for declaration and
333 <item>rebootafterexit
334 <item>ser_apple2_slot
339 <sect1>Hardware access<p>
341 There's currently no support for direct hardware access. This does not mean
342 you cannot do it, it just means that there's no help.
346 <sect>Loadable drivers<p>
348 The names in the parentheses denote the symbols to be used for static linking of the drivers.
351 <sect1>Graphics drivers<p>
355 <tag><tt/a2.lo.tgi (a2_lo_tgi)/</tag>
356 This driver features a resolution of 40×48 with 16 colors.
358 The function <tt/tgi_apple2_mix()/ allows to activate 4 lines of text. The
359 function clears the corresponding area at the bottom of the screen.
361 <tag><tt/a2.hi.tgi (a2_hi_tgi)/</tag>
362 This driver features a resolution of 280×192 with 8 colors and two
363 hires pages. Note that programs using this driver will have to be linked
364 with <tt/-S $4000/ to reserve the first hires page or with <tt/-S $6000/
365 to reserve both hires pages.
367 The function <tt/tgi_apple2_mix()/ allows to activate 4 lines of text. The
368 function doesn't clear the corresponding area at the bottom of the screen.
370 In memory constrained situations the memory from $803 to $1FFF
371 can be made available to a program by calling <tt/_heapadd ((void *) 0x0803, 0x17FD);/
372 at the beginning of <tt/main()/. Doing so is beneficial even if the program
373 doesn't use the the heap explicitly because loading the driver (and in fact
374 already opening the driver file) uses the heap implicitly.
379 <sect1>Extended memory drivers<p>
383 <tag><tt/a2.auxmem.emd (a2_auxmem_emd)/</tag>
384 Gives access to 47.5 KB RAM (190 pages of 256 bytes each) on an Extended
387 Note that this driver doesn't check for the actual existence of the memory
388 and that it doesn't check for ProDOS 8 RAM disk content!
393 <sect1>Joystick drivers<p>
397 <tag><tt/a2.stdjoy.joy (a2_stdjoy_joy)/</tag>
398 Supports up to two standard analog joysticks connected to the game port of
399 the Apple ][.
404 <sect1>Mouse drivers<p>
408 <tag><tt/a2.stdmou.mou (a2_stdmou_mou)/</tag>
409 Driver for the AppleMouse II Card. Searches all Apple II slots
410 for an AppleMouse II Card compatible firmware. The default bounding
411 box is [0..279,0..191].
413 Programs using this driver will have to be linked with <tt/-S $4000/
414 to reserve the first hires page if they are intended to run on an
415 Apple ][ (in contrast to an Apple //e) because the
416 AppleMouse II Card firmware writes to the hires page when initializing
419 Note that the Apple ][ default mouse callbacks support text
425 <sect1>RS232 device drivers<p>
429 <tag><tt/a2.ssc.ser (a2_ssc_ser)/</tag>
430 Driver for the Apple II Super Serial Card. Supports up to 19200 baud,
431 hardware flow control (RTS/CTS) and interrupt driven receives. Note
432 that because of the peculiarities of the 6551 chip transmits are not
433 interrupt driven, and the transceiver blocks if the receiver asserts
434 flow control because of a full buffer.
436 The driver defaults to slot 2. Call <tt/ser_apple2_slot()/ prior to
437 <tt/ser_open()/ in order to select a different slot. <tt/ser_apple2_slot()/
438 succeeds for all Apple II slots, but <tt/ser_open()/ fails with
439 <tt/SER_ERR_NO_DEVICE/ if there's no SSC firmware found in the selected slot.
450 Although the standard binaries generated by the linker for the Apple ][
451 generally run both on DOS 3.3 (with Applesoft BASIC) and on ProDOS 8 (with
452 BASIC.SYSTEM) there are some limitations for DOS 3.3:
456 <tag>Disk file I/O</tag>
457 There's no disk file I/O support. Any attempt to use it yields an error with
458 <tt/errno/ set to <tt/ENOSYS/. This implicitly means that loadable drivers
459 are in general not functional as they depend on disk file I/O. Therefore the statically
460 linked drivers have to be used instead.
463 There's no <tt/interruptor/ support. Any attempt to use it yields the message
464 'FAILED TO ALLOC INTERRUPT' on program startup. This implicitly means that
465 mouse and RS232 device drivers are not functional as they depend on interrupts.
470 <sect1>Direct console I/O<p>
472 The Apple ][ has no color text mode. Therefore the functions
473 <tt/textcolor()/, <tt/bgcolor()/ and <tt/bordercolor()/ have no effect.
476 <sect1>Random number generator<p>
478 The random number seed is generated from the time the program waits for user input.
479 Therefore it is necessary to wait for at least one user keypress either via Standard
480 I/O or via Direct console I/O before initializing the pseudo random number generator.
483 <sect1>Realtime clock<p>
485 There are several types of realtime clocks. It's not desirable to have specific code
486 for all of them. As ProDOS 8 supports file timestamps, realtime clock owners usually
487 use ProDOS 8 drivers for their realtime clock. Those drivers read the realtime clock
488 and write the result to the date/time location in RAM ($BF90 to $BF93).
489 ProDOS 8 reads the date/time from that RAM location. If there's no realtime clock the
490 RAM location keeps containing zeros. ProDOS 8 uses those zeros as timestamps and the
491 files show up in a directory as <tt/<NO DATE>/.
493 There's no common interface to set realtime clocks so if a realtme clock <bf/IS/
494 present there's just nothing to do. However, if there's <bf/NO/ realtime clock present,
495 the user might very well be interested to "manually" set the RAM location in order to
496 have timestamps. But he surely doesn't want to manually set the RAM location over and
497 over again. Rather he wants to set it just once after booting ProDOS 8.
499 From that perspective it makes most sense to not set both the date and the time but
500 rather only set the date and have the time just stay zero. Then files show up in a
501 directory as <tt/DD-MON-YY 0:00/.
503 So <tt/clock_settime()/ checks if the current time equals 0:00. If it does <bf/NOT/
504 then a realtime clock is supposed to be active and <tt/clock_settime()/ fails with
505 <tt/ERANGE/. Otherwise <tt/clock_settime()/ sets the date - and completely ignores
506 the time provided as parameter.
508 <tt/clock_getres()/ too checks if the current time equals 0:00. If it does <bf/NOT/
509 then a realtime clock is supposed to be active and <tt/clock_getres()/ returns a time
510 resolution of one minute. Otherwise <tt/clock_getres()/ presumes that the only one
511 who sets the RAM location is <tt/clock_settime()/ and therefore returns a time
512 resolution of one day.
519 <sect1>Passing arguments to the program<p>
521 Command line arguments can be passed to <tt/main()/ after BLOAD. Since this is not
522 supported by BASIC, the following syntax was chosen:
525 ]CALL2051:REM ARG1 " ARG2 IS QUOTED" ARG3 "" ARG5
529 <item>Arguments are separated by spaces.
530 <item>Arguments may be quoted.
531 <item>Leading and trailing spaces around an argument are ignored. Spaces within
532 a quoted argument are allowed.
533 <item>The first argument passed to <tt/main/ is the program name.
534 <item>A maximum number of 10 arguments (including the program name) are
541 The runtime for the Apple ][ uses routines marked as
542 <tt/.INTERRUPTOR/ for ProDOS 8 interrupt handlers. Such routines must be
543 written as simple machine language subroutines and will be called
544 automatically by the interrupt handler code when they are linked into a
545 program. See the discussion of the <tt/.CONDES/ feature in the <url
546 url="ca65.html" name="assembler manual">.
554 The function <url url="dio.html#s1" name="dio_open()"> has the single
555 parameter <tt/device/ to identify the device to be opened. Therefore an
556 Apple II slot and drive pair is mapped to that <tt/device/ according
560 device = slot + (drive - 1) * 8
563 so that for example slot 6 drive 2 is mapped to <tt/device/ 14.
566 The function <url url="dio.html#s3" name="dio_query_sectcount()"> returns
567 the correct sector count for all ProDOS 8 disks. However for any non-ProDOS 8
568 disk it simply always returns 280 (which is only correct for a 140 KB disk).
569 This condition is indicated by the <tt/_oserror/ value 82.
574 <sect1>Specifying file types for fopen<p>
578 <tag>Explanation of File Types</tag>
580 ProDOS associates a file type and an auxiliary type with each file.
581 These type specifications are separate from the file's name, unlike
582 Windows which uses the file name's suffix (a.k.a.
583 extension) to specify the file type. For example, <tt/.exe/,
584 <tt/.doc/, or <tt/.bat/.
586 Machine-Language Interface (MLI) functions for creating and opening
587 files require these types to be specified. And if they don't match
588 with the file being opened, the operation may fail.
590 In contrast, the ISO C function <tt/fopen()/ and the POSIX function
591 <tt/open()/ have no parameter to specify either a file type or an
592 auxiliary type. Therefore, some additional mechanism for specifying
593 the file types is needed.
595 <tag>Specifying the File Type and Auxiliary Type</tag>
597 There are two global variables provided that allow the file type
598 and auxiliary type to be specified before a call to <tt/fopen()/
599 or <tt/open()/. They are defined in <tt/apple2_filetype.h/:
603 extern unsigned char _filetype; /* Default: PRODOS_T_BIN */
604 extern unsigned int _auxtype; /* Default: 0 */
608 The header file <tt/apple2_filetype.h/ also defines many values
609 that can be used to set these variables. It is included in
610 <tt/apple2.h/, which is in turn included in <tt/apple2enh.h/.
611 So it isn't necessary to include it directly. Just
612 include one of <tt/apple2.h/ or <tt/apple2enh.h/.
616 A text file cannot be created with just the
617 standard C functions because they default to the binary type
618 <tt/PRODOS_T_BIN/. The <tt/_filetype/ variable must be set to
619 <tt/PRODOS_T_TXT/ to create a text file.
622 <tt/_auxtype/ specifies the record length. A zero record
623 length text file is referred to as a sequential text file.
624 This is equivalent to text files on
625 other operating systems, except that the line terminator is a
626 carriage return instead of a line-feed (Linux/BSD/MacOS) or
627 carriage return, line-feed pair (Windows).
629 The "sequential" text file terminology is in contrast to a
630 "random-access" text file which would
631 have a fixed-length, non-zero record length, so that the
632 file position of any individual record can be calculated.
634 For this example, the
635 <tt/_auxtype/ does not need to be set because it defaults to
636 the desired value, which is zero. To be more explicit,
637 <tt/_auxtype/ can also be set to <tt/PRODOS_AUX_T_TXT_SEQ/
638 which is defined as zero.
642 #include <stdio.h>
643 #include <string.h>
644 #include <errno.h>
645 #include <apple2.h>
650 char *name = "MY.FAVS";
652 /*-----------------------------*/
654 _filetype = PRODOS_T_TXT;
655 _auxtype = PRODOS_AUX_T_TXT_SEQ;
657 /*-----------------------------*/
659 if ((out = fopen(name, "w")) != NULL) {
660 fputs("Jorah Mormont\r", out);
661 fputs("Brienne of Tarth\r", out);
662 fputs("Daenerys Targaryen\r", out);
663 fputs("Sandor Clegane\r", out);
664 if (fclose(out) == EOF) {
665 fprintf(stderr, "fclose failed for %s: %s", name, strerror(errno));
669 fprintf(stderr, "fopen failed for %s: %s", name, strerror(errno));
680 This software is provided 'as-is', without any expressed or implied
681 warranty. In no event will the authors be held liable for any damages
682 arising from the use of this software.
684 Permission is granted to anyone to use this software for any purpose,
685 including commercial applications, and to alter it and redistribute it
686 freely, subject to the following restrictions:
689 <item> The origin of this software must not be misrepresented; you must not
690 claim that you wrote the original software. If you use this software
691 in a product, an acknowledgment in the product documentation would be
692 appreciated but is not required.
693 <item> Altered source versions must be plainly marked as such, and must not
694 be misrepresented as being the original software.
695 <item> This notice may not be removed or altered from any source