fswrit(vun.i2.r, io_buffer.i1a.r, num_bytes.i2.r, status.i2.r	     
	       [,ext_status.i4.r] [,record_number.i4.r] [,event_flag.i2.r]
	       [,timeout.i2.r] [,nomod.i2.r] [,nodesc.i1.r] [,astfunc.f.v])
	File Sharing service routine used to write a record to a file opened 
	on the virtual unit number.  The file may have either sequential or	
	relative organization and fixed or variable length records.  The     
	record is gotten into the user's buffer according to the number	     
	number of bytes specified.  If the file was opened with direct	     
	access, then the logical record number defines the record to be	     
	written.  If the file was opened with sequential access, then the    
	next record in sequence is written.  If an event flag (non-zero) or
	AST function is specified, then the write will be done asynchronously
	and control will be returned to the user before the write is complete.

	vun		virtual unit number on which the file was opened
	io_buffer	user's record buffer containing the record to be
	num_bytes	size of the record to be written in bytes
	status		returned ACNET status code
	[ext_status]	returned extended status from VMS/RMS (default is NULL)
	[record_number]	logical record number for files opened for direct
			access (default is next sequential record)
	[event_flag]	I/O completion event flag number    
			(write is asynchronous if this is specified and
			 non-zero) (default is NULL)
	[timeout]	user-specified network timeout interval in units
			of seconds (default is 10 seconds)
	[nomod]		switch which specifies, if TRUE, that the record
			to be written is NOT to be modified if it already
			exists.  TRUE disables record modifications.  The
			default of FALSE permits existing records to be
			modified.  New records are always written.
	[nodesc] 	switch to identify the characteristics of 'iobuf'
			(TRUE -> "io_buffer" is treated as a byte buffer passed
				 by reference,
			 FALSE -> "io_buffer" is treated as a character string
				  descriptor (default))
	[astfunc]	specifies the address of a routine to be executed
			at AST level on I/O completion (read is asynchronous
			if this is specified and non-zero) (default is NULL)

	This function requires the following include files:

	cnsparam_h, clib_h

	Related functions:

	fsopen, fsclos, fsread, fsunlk, fsrdm, fsrew, fsweof, fsdel