Predefined CPP Macros when targetting platforms
-----------------------------------------------

cc65 uses upper case:

__CC65__   __ATMOS__   __APPLE2__

GNU C uses lower case, in addition to the nonstanded nonunderlined lables:

__unix__   __vax__     __m68k__

Microsoft C uses *one* underline at the *start* only:

_WIN32     _MSDOS      _DLL

Arrggh!

I have chosen to use a single start file for each platform and have that
define macros to specify the platform. Thus to compile software written by
me to target the Windows 32-bit platform, compile win32.c and it will define
macros and chain off to the rest of the source.

Within my source I have used __(lowercase)__ to specify platform and
__(lowercase)_h to specify an included file. For example:

Macro      Target
__bbc__    Acorn BBC/Master series
__apple2__ Apple II
__riscos__ RISC OS (including Arthur)
__unix__   Unix/Linux/etc
__win32__  32bit Windows
__dos__    80x86 DOS
__cpm__    8080/Z80 CP/M
__6502__   6502 series cpu
__i86__    Intel 80x86 cpu
__z80__    Zilog Z80 cpu
__arm__    ARM RISC cpu
__m86000__ Motorola 860x0 cpu

__console_h console.h has been #included
__ziplib_h  ziplib.h has been #included

So, for example, bbc.c may include:
----bbc.c----
*/ bbc.c - Compile to target Acorn BBC/Master */

#ifndef __bbc__
#define __bbc__
#endif
#ifndef __6502__
#define __6502__
#endif

#include "src/prog.c"
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