'C' Libraries for targetting the BBC I/O
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                         Version 1.00 - 12-Jun-2005
                      <bbc/os.h> functions and macros

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void os_cli(char *s);
	char *s		string to pass to OSCLI
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int os_fx(int a, int x, int y)
	int a		OSBYTE function in A
	int x		OSBYTE X value
	int y		OSBYTE Y value

	Returns value in X.
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int os_byte(int a, int xy)
	int a		OSBYTE function in A
	int XY		OSBYTE X and Y values

	Returns X+256*Y, ie the value held in XY.
	Note: returned Carry is lost.
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int os_word(int a, char *xy)
	int a		OSWORD function in A
	char *xy	pointer to control block in XY

	Returns value in Y.
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void os_wrch(int ch)
	int ch;		character sent to OSWRCH in A
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int os_rdch(void);

	Returns A in low byte and Carry in second byte.
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int os_file(int a, char *name, char *block);
	int a		OSFILE function in A
	char *name	filename
	char *block	OSFILE control block in XY

	Returns filetype in A.
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long os_args(int a, int handle, long arg);
	int a		OSARGS function in A
	int handle	file handle in Y
	long arg	argument to write, or zero to read

	Returns the new argument.
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int os_bget(int handle);
	int handle	file handle in Y

	Returns A in low byte and Carry in second byte.
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int os_bput(int ch, int handle);
	int ch		character to BPUT in A
	int handle	file handle in Y
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int os_gbpb(int a, int handle, char *block);
	int a		OSGBPB function in A
	int handle	file handle in block[0]
	char *block	address of control block in XY

	Returns A in low byte and Carry in second byte.
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int os_find(int a, char *name);
	int a		OSFIND function in A
	char *name	filename

	Returns file handle in A
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void os_close(int handle);
	int handle	OSFIND handle in Y
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char *os_report(void);

	Returns address of error block from &FD/&FE.
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void os_error(int err, char *s);
	int err		error number
	char *s		error string

	Generates a BRK error.
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int os_escape(void);

	Returns the escape state from &FF
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void os_onerror(void *f());
	void *f()	function to jump to when an error occurs, or NULL
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char *os_call(char *regs);
	char *regs	register block A,X,Y,P,PC

	Returns pointer to a register block holding A,X,Y,P
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int os_host(void)
	Returns the current BBC host type, as follows:

Note: provisional, will be changed
#define _kernel_HOST_UNDEFINED    -1
#define _kernel_BBC_MOS1_0         0
#define _kernel_BBC_MOS1_2         1
#define _kernel_BBC_ACW            2
#define _kernel_BBC_MASTER         3
#define _kernel_BBC_MASTER_ET      4
#define _kernel_BBC_MASTER_COMPACT 5
#define _kernel_ARTHUR             6
#define _kernel_RISC_OS            6
#define _kernel_SPRINGBOARD        7
#define _kernel_A_UNIX             8
#define _kernel_SPECTRUM          31
#define _kernel_PC                32
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#define __bbc__
	Macro defined when targetting the BBC platform
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