(***************************************************************************
	OPEN <FILE NAME> <MODE> <FILE CONTROL BLOCK>

FILE NAME:
    Legal CP/M file name. <14 characters max>
    LST:    = PRINTER;
    CON:    = CONSOLE;

MODE:
    I = INPUT;		O = OUTPUT;		    R = RANDOM;
*DIRECTION***
input from	      output to 		     random I/O
from disk/console     disk/console/printer
*IORESULT***
FALSE - 		FALSE - 		     FALSE -
  file does not exist	  file already exists	       file does not exist, so
			  could not open file	       created file for write.
TRUE -			     TRUE -		     TRUE -
  file exists.		  created file for write       found requested file.

FILE CONTROL BLOCK:
    file control block/file variable;
***************************************************************************)
PROCEDURE OPEN ( FileName: DSTRING; MODE: CHAR; VAR FCB: TEXT );
LABEL	1; { fatal error exit }
CONST	idlen = 14; { max allowed chars for legal CP/M file name }
VAR	ipos: integer;
	flag: CHAR;
BEGIN
  con_wanted := false;				{ * initialize flags * }
  printer_wanted := false;
  case mode of					{ * determine direction * }
	'I': {input file}      flag := '<';
	'O': {output file}     flag := '>';
	'R': {random IO}       flag := 'R';
	else: begin {invalid MODE specified }
		writeln('+++INVALID MODE');
		ioresult := false;
		{EXIT} goto 1
	      end
  end{case};
  if pos('<|',filename)<>0 then  { * determine default file names * }
    filename := 'PIPE.A'
  else if pos('>|',filename)<>0 then
    filename := 'PIPE.B'
  else if pos('CON:',filename)<>0 then begin
    filename := 'CON:';
    con_wanted := true
  end
  else if pos('LST:',filename)<>0 then begin
    filename := 'LST:';
    printer_wanted := true
  end
  else begin
    ipos := pos(flag,filename);
    if ( ipos<>0 ) then { a file name was specified }
       filename := copy(filename,ipos+1,length(filename)-ipos+1);
  end;

  if length(filename) > idlen then begin
    { length of file name exceeds requirements }
    writeln('+++INVALID FILE NAME: ', filename);
    ioresult := false;
    {EXIT} goto 1
  end;

   case mode of
   'I': { OPEN file FileName for READ assign FCB }
	begin
	  if ( filename='LST:' ) then { error - printer is output device }
	    ioresult := false
	  else if ( filename='CON:' ) then begin
	    RESET(filename, fcb);
	    ioresult := true;
	  end
	  else begin
	    RESET(filename, fcb);
	    ioresult := not eof(fcb)
	  end
	end;

   'O': { OPEN file filename for WRITE assign FCB }
	begin
	  if ( filename='CON:' ) OR ( filename='LST:' ) then begin
	    REWRITE(filename, fcb);
	    ioresult := true
	  end
	  else begin { * file must NOT already exist * }
	    reset(filename,fcb);       { * see if file already exists * }
	    if not eof(fcb) then begin { report error }
	      writeln('+++FILE "', filename, '" EXISTS');
	      ioresult := false
	    end
	    else begin { file does not exist }
	      rewrite(filename,fcb);
	      ioresult := true
	    end
	  end
	end;

   'R': { OPEN FILE FILENAME FOR RANDOM IO ASSIGN FCB }
	  begin
	    reset(filename,fcb);    { * see if file already exists * }
	    if not eof(fcb) then { file exists }
	      ioresult := true
	    else begin { file does not exist so create it }
	      rewrite(filename,fcb);
	      ioresult := false
	    end
	  end;
   end{case};
1: { fatal error exit }
END{ OF OPEN };



te(filename,fcb);
	      ioresult := false
	    end
	  end;
   end{case};
1: { fatal error exit }
END{ OF OPEN