Added atmos and new c16 target

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<article>

<title>cc65 Library Overview
<author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">
<date>02.12.2000

<abstract>
An overview over the runtime and C libraries that come with the cc65 compiler,
including a discussion of the differences to the ISO standard.
</abstract>

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<sect>Overview<p>

This file contains a description of the library routines available for the
cc65 C compiler. It is not complete in some areas, so if you miss something,
have a look into the header files. All functions, that are not defined by the
ISO C standard have a short comment in the headers, explaining their use.



<sect>ISO C compatible library<p>

The C library contains a large subset of the ISO C library. Functions are
usually missing in areas, where there is no support on typical 6502 systems.
Wide character sets are an example for this.

I will not go into detail about the ISO functions. If a function is not
mentioned here explicitly, expect it to be available and to behave as defined
in the C standard.

Functions that are NOT available:

<itemize>

  <item>ftell/fseek/fgetpos/fsetpos

  <item>tmpfile/tmpnam

  <item>The scanf family of functions

  <item>time/asctime/ctime/difftime/asctime/gmtime/localtime/mktime/strftime

  <item>system

  <item>All functions that handle floating point numbers in some manner.

  <item>The div and ldiv functions (because cc65 is not able to return
    structs).

  <item>All functions handling wide character strings.

  <item>Signals and all related functions (having SIGSEGV would be cool:-)

  <item>rename/remove/rewind

  <item>setbuf/setvbuf/ungetc

</itemize>

Functions that are limited in any way:

<itemize>

  <item>fopen/fread/fwrite/fclose/fputs/fgets/fscanf....

  These functions are built on open/read/write/close. Neither of these low
  level functions is currently available for the supported systems, and so,
  fopen and friends do not work. However, the functions exist and are tested
  to some degree under the ACE operating systems (which is no longer
  supported).


  <item>strcspn/strpbrk/strspn

  These functions have a length limitation of 256 for the second string
  argument. Since this string gives a character set, and there are only 256
  distinct characters, this shouldn't be a problem.


  <item>getenv

  Since there is no such thing as an environment on all supported systems, the
  getenv function will always return a NULL pointer.


  <item>locale

  There is no other locale than the "C" locale. The native locale is identical
  to the "C" locale.

</itemize>


In addition to these limitations, some more functions are limited if inlined
versions are requested by using -Os:

<itemize>

  <item>The strlen function only works for strings with a maximum length of
  255 characters.

  <item>The isxxx character classification functions from <tt/&lt;ctype.h&gt;/
  will give unpredictable results if the argument is not in character range
  (0..255). This limitation may be removed by #undef'ing the function name
  (when using -Os, the functions are actually macros that expand to inline
  assembler code, but the real functions are still available if the macro
  definition is removed).

</itemize>



<sect>CPU specific stuff - 6502.h<p>

The header file 6502.h contains some functions that make only sense with the
6502 CPU. Examples are macros to insert more or less useful instructions into
your C code, or a function to call arbitrary machine language subroutines,
passing registers in and out.



<sect>Target specific stuff<p>

For each supported system there's a header file that contains calls or defines
specific for this system. So, when programming for the C64, include c64.h, for
the C128, include c128.h and so on. To make the task for the Commodore systems
easier, there is also a header file named cbm.h that will define stuff common
for all CBM systems, and include the header file for the specific target
system.

The header files contain

<itemize>

  <item>Defines for special keys (like function keys)

  <item>Defines for special characters (like the graphics characters)

  <item>Variables with a fixed address in memory that may be used to access
  special hardware. For the C64 and C128 there is a variable struct named
  <tt/SID/. Writing to the fields of this struct will write to the SID device
  instead. Using these variables will make your program more readable and more
  portable. Don't fear ineffective code when using these variables, the
  compiler will translate reads and writes to these structs into direct memory
  accesses.

  <item>Other routines that make only sense for a specific system. One example
  are routines to write memory locations in the system bank for the CBM PET-II
  family.

</itemize>


<sect>Direct console I/O - <tt/conio.h/<p>

The <tt/conio.h/ header file contains a large set of functions that do screen
and keyboard I/O. The functions will write directly to the screen or poll the
keyboard directly with no more help from the operating system than needed.
This has some disadvantages, but on the other side it's fast and reasonably
portable. conio implementations exist for the following targets:

  <itemize>
  <item>atari
  <item>c16 (works also for the c116 with up to 32K memory)
  <item>c64
  <item>c128
  <item>plus4
  <item>cbm510 (40 column video)
  <item>cbm610 (all CBM series-II computers with 80 column video)
  <item>pet (all CBM PET systems except the 2001)
  <item>apple2
  </itemize>

The conio.h header file does also include the system specific header files
which define constants for special characters and keys.



<sect>Using the joystick - <tt/joystick.h/<p>

For systems that have a joystick, <tt/joystick.h/ will define a subroutine to
read the current value, including constants to evaluate the result of this
function. To help in writing portable code, the header file will define the
symbol <tt/__JOYSTICK__/ on systems that have a joystick.



<sect>Using a mouse - <tt/mouse.h/<p>

Some target machines support a mouse. Mouse support is currently available for
the following targets:

  <itemize>
  <item>atari
  <item>c64
  <item>c128
  <item>cbm510
  </itemize>

The available functions are declared in <tt/mouse.h/ To help writing portable
code, the header file will define the symbol <tt/__MOUSE__/ in systems that
support a mouse.


<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>Copyright<p>

This C runtime library implementation for the cc65 compiler is (C)
Copyright 1998-2001 Ullrich von Bassewitz. For usage of the binaries
and/or sources the following conditions do apply:

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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