The STATUS function indicates the status of a file following the
  last operation performed on it.

  Syntax:

     STATUS( file_variable )

  The 'file_variable' is the name of the file variable  associated
  with the file to be tested.

  The file can be in any mode before STATUS is called;  unless  an
  error  occurs,  STATUS  does  not  change  the  file  mode  upon
  execution.

  The  STATUS  function  returns  integer  codes  indicating   the
  previous  operation's  effect  on the file.  If the operation is
  successful, 0 is returned.  If end-of-file is encountered, -1 is
  returned.   If  an  error  is encountered, a positive integer is
  returned.  (The actual  number  is  environmental  specific  and
  indicates the exact error that occured.)

  A test by the STATUS function on  a  TEXT  file  causes  delayed
  device  access  to  occur, thus filling the file buffer with the
  next file component.  Therefore,  EOF,  EOLN,  UFB,  and  STATUS
  never  return  an  error  code  following  a  successful  STATUS
  function call.

  See the "HP Pascal Language Reference  Manual"  for  a  complete
  description of the STATUS function.