Arguments

 
  filename = name of file to open 

  flags    = 1 character indicating read (R) or 
             write (W). Opening an existing file 
             for write first truncates the file. 
             Opening a non-existent file for read 
             results in an error.
 
  handle   = variable to hold a pointer to the open file
 
  buffer   = buffer into which an event is read (evRead) 
             or from which an event is written(evWrite). 
             The first word of the buffer will/should 
             contain the event length in longwords excluding 
             the length word. On a read if the event is 
             longer than the buffer length, only buflen 
             words are written to the buffer, and an error 
             is returned. 

  buflen   = length of caller's buffer in longwords 

  request  = I/O request option: 
             "B" or "b": change the blocksize 
             of physical records 

  argp     = value for I/O request