S_DR

 Function
  Set the share deny read flag in a FCREATE/FOPEN/FAPPEND statement.

 Value
  1 = 1b = 1o = 1h

 Remarks
  DOS 3.1 or later (which is what is required by PCBoard) allows processes
  to decide what mode of file sharing should be allowed.  This constant
  allows you to specify that other processes may open the same file, but
  that they may not open it for read access, from the time you open the
  file to the time you close the file.

 Example

  FOPEN 1,"FILE.DAT",O_RD,S_DR ' Deny other processes read access
  FOR i = 1 TO 10
   FGET 1,s
   PRINTLN s
  NEXT
  FCLOSE 1 ' Close the file and allow others to open it in any mode