Low Level File Entry Points
			===========================


BOSFILEb					  File and directory information

Entry address: &FFDD

On entry:  A	function code		  On exit:  A	object type
           XY	pointer to control block	    XY	preserved
						    control block updated
If function not supported, A is returned preserved.

Control block:
 &00  Address of filename
 &02  Load address
 &06  Execution address
 &0A  Length, or start address for SAVE
 &0E  Attributes, or end address for SAVE
 &12

Functions:
 &FD Read file system information (System Internal Name).  The attribute
     field is returned holding the sector start address.
 &FE Verifies file.  Control block is as for A=&FF, Load.  If the
     verification is successful, A is returned holding &01 and the control
     block holds the file information.  If the verification fails, A is
     returned holding &00 and the load address is returned holding the
     address where the verification failed.  If the file does not exist or
     is a directory or does not have read access, then an error is
     generated.  
 &FF Loads a file into memory.  If the low byte of the execution address
     is zero, the file's own load address is used, else the supplied
     address is used to load to.  If the filename does not exist, or is a
     directory, or an execute-only file, or does not have read access,
     then an error is generated.
 &00 Save a file.  If a file already exists with the same name, it is
     overwritten, with the file access staying the same, but the case of
     the name being the new name.  If the file is locked, or a directory
     exists with the same name, then an error is generated.
 &01 Writes a file's reload address, execution address and attributes.
 &02 Writes a file's reload address.
 &03 Writes a file's execution address.
 &04 Writes a file's attributes.
 &05 Read object's catalogue information into the control block.
 &06 Delete object.  If the object does not exist, A returned as &00.  If
     the object is locked, or is not owned, then an error is generated.
 &07 Create an empty file of defined length.  Block as for SAVE.
 &08 Create a directory.  If a directory already exists, there is no
     error.  The created directory is locked.  If a file already exists,
     an error is generated.
 &09

Object types returned in the A register are:
	&FF Execute-only file
	&00 Object not found
	&01 File found
	&02 Directory found








File attributes:   These are held in four bytes as follows:
Byte   &0E   bit 7   Privatised
		  6   Execute only by others
		  5   Writable by others
		  4   Readable by others
		  3   Locked
		  2   Execute only for owner
		  1   Writable by owner
		  0   Readable by owner
Byte   &0F bits 0-4  Date: day of month
		 5-7  Date: year since 1981, bits 4-6
Byte   &10 bits 0-3  Date: month of year
		 4-7  Date: year since 1981, bits 0-3
Byte   &11 bits 0-7  Undefined (zero)


BOSFINDb					  Open or close a file

Entry address:	&FFCE

On entry:  A   function code		  On exit:  A   channel number, or
	    Y	channel number for A=0 or               0 if no file opened
	    XY  pointer to filename                 XY  preseved
If function not supported, A is returned as zero.

Functions:
 &00  Close the file on channel in Y.  If Y=0 then close all files.
 &4X  Open file for input.
 &8X  Open file for output.  If file already exists, tries to delete it
	first.  If no file exists, a file is created with load and
	execution addresses set to &FFFFFFFF.
 &CX  Open file for update.  If no file exists, A is returned with 0.
The bottom four bits of A control how the file is opened:
 If b3 is set, returns an error if file not found, instead of zero handle.
 If b2 is set, error is generated if attempt to open a directory.


BOSBGETb					  Read (get) a byte

Entry address:	&FFD7

On entry:  Y	channel number		  On exit:  A   byte read
						    Y   preserved
						    Cy  EOF status.

If the byte read is after the end of file, the carry flag is set on exit
and the EOF-error-flag is set.  After the EOF byte has been read, the next
read produces an error.  An error is generated if the object is a
directory or doesn't have read access.


BOSBPUTb					  Write (put) a byte

Entry address: &FFD4

On entry:  A	byte to be written	  On exit:  All preserved
	    Y	channel number

An error is generated is the object is a directory or doesn't have write
access.  The EOF-error-flag is cleared.






BOSARGSb					  Attribute of open object

Entry address: &FFDA

On entry:  A   function code		  On exit:  A  see below
	    X   points to zero page location        X  preserved
	    Y   file handle or 0                    Y  preserved
If function not supported, A is returned preserved.

Functions:
   Y=0
 &FD HADFS: Return version number and capabilities to zero page.
 &FE Return last drive used.
 &FF Update all files to media.
 &00 Return filing system number in A:
	 0 No current filing system		20 RawKbd:
	 1 1200 baud cassette filing system	21 DeskFS:
	 2 300 baud cassette filing system	22 Computer Concepts RomFS:
	 3 ROM filing system			23 RamFS:
	 4 Disk filing system			24 RISCiXFS:
	 5 Econet network filing system		25 Streamer:
	 6 Teletext/Prestel telesoftware	26 SCSIFS:
	 7 IEEE filing system			27 Digitiser:
	 8 Acorn ADFS				28 Scanner:
	 9 Host filing system			29 MultiFS:
	10 Videodisk filing system
	11					33 NFS:
	12 Ram filing system	NetPrint:	37 CDFS:
	13			Null:		43 DOSFS:
	14			Printer:	46 ResourceFS:
	15 			Serial:		47 PipeFS:
	16 Harston ADFS
	17			Vdu:		53 DeviceFS:
	18			RawVdu:		54 Parallel:
	19			Kbd:
      Extra Archimedes filing systems are suffixed with B:b.
 &01 Return address of any parameters after a filename to zero page.
 &02 Return version number in A.
 &03 Return libfs number in A.
 &04 Return disk space used to zero page.
 &05 Return disk free space to zero page.

   Y<>0
 &FD HADFS: Read or set context.
 &FE Arch: Read info on file handle.
 &FF Update file on channel Y to media.
 &00 Read PTR for channel Y to zero page.
 &01 Write PTR for channel Y from zero page.  If PTR is moved past the end
	of an output file, the file is extended with zeroes and zero
	returned in A.  If PTR is moved past the end of an input file, an
	error is generated.  The EOF-error-flag is cleared.
 &02 Read EXT for channel Y to zero page.
 &03 Write EXT for channel Y.  If the length of the file is reduced, the
	end disappears.  If the length is increased, the file is extended
	as with &01 and zero is returned in A.  The EOF-error-flag is
	cleared.
 &04 Read size allocated to file on channel Y to zero page.
 &05 Read EOF status for channel Y.  If PTR=EXT then zero page is set to
	-1, else zero page is set to 0.
 &06 Ensure file size of at least the value in zero page.  Actual size
	allocated is returned in zero page.
 &07 Arch: convert file handle to filename.  Zero page points to buffer.
 &08 Arch: informs of change in image stamp.

If zero page is not used, then it is ignored and so X may be left set to
anything on entry.
BOSGBPBb					  Read or write multiple bytes

Entry address:	&FFD1

On entry:  A	function code		  On exit:  A   see below
	    XY	pointer to control block            XY	preserved
						    control block updated
If function not supported, A is returned preserved.

Control block:
 &00  Channel number/cycle number or zero
 &01  Data address
 &05  Number of bytes/filenames to transfer
 &09  PTR for transfer/directory pointer
 &0D

Functions:
 &01  Write bytes to media using new PTR.  If XY+0 is 0, undefined.
 &02  Write bytes to media ignoring new PTR.  If XY+0 is 0, undefined.
 &03  Read bytes from media using new PTR.  If XY+0 is 0, undefined.
 &04  Read bytes from media ignoring new PTR.  If XY+0 is 0, undefined.
   On exit from calls &01 to &04 the 'number of bytes' field  holds the
   number of bytes not transfered.  The 'data address' field is updated to
   point to the next location for data transfer.  The PTR for the file is
   updated by the number of bytes transfered and placed in the 'PTR'
   field.  In functions &01 and &03 the PTR is first set to the supplied
   value before transfering data.  The carry flag is returned set if EOF
   was met.  The EOF-error-flag is reset.  An error occurs if the object
   is a directory or does not have the correct access.
 &05  Get media title of CSD disk and boot option into data block:
	    &00 length of title (n) 
	    &01 title in ASCII characters
	  &01+n startup option
	  &02+n drive number
	  &03+n
 &06  Get currently selected directory name into data block:
	    &00 length of drive identity (n)
	    &01 ASCII drive identity (drive number)
	  &01+n length of directory name (m)
	  &02+n directory name in ASCII characters
	&02+n+m ownership: &00 - owner, &FF - public	
	&03+n+m
 &07  Get current library name into data block:
	    &00 length of drive identity (n)
	    &01 ASCII drive identity (drive number)
	  &01+n length of library name (m)
	  &02+n library name in ASCII characters
	&02+n+m ownership: &00 - owner, &FF - public
	&03+n+m
 &08  Read filenames from current directory into data block:
	    &00 length of filename 1 (n)
	    &01 filename 1 in ASCII characters
	  &01+n length of filename 2 (m)
	  &02+n filename 2 in ASCII characters
	&02+n+m etc...
   The first call to function &08 should be made with the directory
   pointer set to zero.  This will read the first filename, and the
   pointer will be updated so that the next call will read the next
   filename.  When no filenames are left, the call returns with the
   'number of filenames' left unchanged and the carry flag set.    






 &09  Reads work/login filename, command line tail or entries from
   specified directory.  If XY+0 is zero, reads work/login filename or
   command tail:
	    &00	length of drive identity or command line tail (n)
	    &01	ASCII drive identity (drive number) or comand line tail
	  &01+n	length of work/login filename (m)
	  &02+n	work/login filename
	&02+n+m
   If XY+0 is a channel number of an open directory, reads a null-
   terminated list of directory entries.  The function is called as for
   OSGBPB 8, but XY+5 returns the number of filenames read.
 &0A  Read entries and information from the opened directory whose channel
   number is in XY+0.  This function is called as for OSGBPB 9.  Each
   record is a whole multiple of four bytes long:
	    &00	Load address
	    &04	Execution address
	    &08	Length
	    &0C	Attributes
	    &10	Object type (1=file, 2=directory)
	    &14	Object name, null terminated
	    xxx	next record 
 &0B  Read entries and information from the opened directory whose channel
   number is in XY+0.  This function is called as for OSGBPB 9.  Each
   record is a whole multiple of four bytes long:
	    &00	Load address
	    &04	Execution address
	    &08	Length
	    &0C	Attributes
	    &10	Object type (1=file, 2=directory)
	    &14	Sector start address
	    &18	Five zeros (reserved for centisecond time since 1900)
	    &1D	Object name, null terminated
	    xxx	next record


BFSCVb					  Filing system control

This vector is only called by the operating system, and should not be
called directly.  This list just shows the full list of calls.

Functions:
 &00  *OPT command.  X and Y hold parameters
 &01  EOF being checked with Osbyte &7F.  On exit, X=&FF if EOF, X=&00
	otherwise.
 &02  */ command.  XY points to the command text.  HADFS tries to run the
	command from the CSD or the LIB.
 &03  Unrecognised Oscli.  XY points to the command text.  HADFS checks
	the command against its own commands, then tries to run it from
	disk as with function &02.  
 &04  *RUN command.  XY points to filename.  HADFS tries to run this from
	the CSD only.
 &05  *CAT command.  XY points to any pathname.
 &06  A new filing system is about to take over.  This call is generated
	by filing systems themselves before they start their
	initialisation.
 &07  File handle range request.  Lowest returned in X, highest in Y. 
 &08  Oscli command being processed.  This is used to facilitate the
	*ENABLE command.
 &09  *EX command.  XY points to any pathname.
 &0A  *INFO command.  XY points to the filename.
 &0B  *RUN from library.  XY points to the filename.
 &0C  *RENAME command.  XY points to the filenames after the command.