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    FileSHARinG !

    When sharing Files concurrently, by means of For example a multitasker or a
    network, it is necessary to use the File sharing as provided by the Dos
    command SHARE, or as provided by a Network shell (In Novell File sharing is
    supported by the network shell on Servers, not locally. Check your network
    documentation For more inFormation).

    File sharing is simple in TP/BP, since the system Variable FileMode defines
    in what mode a certain File is opened in:

    Const
       fmReadOnly  = $00;  (* *)
       fmWriteOnly = $01;  (* Only one of these should be used *)
       fmReadWrite = $02;  (* *)

       fmDenyAll   = $10;  (* together With only one of these  *)
       fmDenyWrite = $20;  (* *)
       fmDenyRead  = $30;  (* *)
       fmDenyNone  = $40;  (* *)

       fmNoInherit = $70;  (* Set For "No inheritance"         *)

    Construction the FileMode Variable is easy, just add the appropriate values:

    FileMode:=fmReadOnly+fmDenyNone;
          (Open File For reading only, allow read and Write.)

    FileMode:=fmReadWrite+fmDenyWrite;
          (Open File For both read and Write, deny Write.)

    FileMode:=fmReadWrite+fmDenyAll;
          (Open File For both read and Write, deny all.)

    Say you open the File in "fmReadWrite+fmDenyWrite". This will let you read
    and Write freely in the File, While other processes can freely read the File.
    if another process tries to open the File For writing, that process will get
    the error "Access denied".

    (fmNoInherit is seldom used - it defines if a childprocess spawn from your
    process will be able to use the Filehandle provided by your process.)

    The FileMode Variable is only used when the File is opened;

     ...
    Assign(F,FileName);
    FileMode:=fmReadOnly+fmDenyNone;
    Reset(F);
    FileMode:=<Whatever>    (* Changing FileMode here does not affect the
                               Files already opened *)

    By default, FileMode is defined as FileMode:=$02 in TP/BP, this is referred
    to as "Compatibility mode" in the TP/BP docs. Two processes accessing the
    same File With this Filemode results in the critical error "Sharing
    violation".
    ----------------------------------------------------------------------

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