{$X+} Program Indexd(indexed:' ',input,output);
{test PDP8 Pascal indexed I/O facility	 JTE  1081-08-26}
const maxword = 00377b {determines LRL}; {$L-}
  prompt = '[Rn,Wn,L,Q]: ';
var
  indexed: file[1..4095] of array[0..maxword] of 0..7777b;
  index, lastindex, maxindex: integer; ch: char;
  quit: boolean; fn: packed array[1..14] of char;

  procedure reportfile;
  begin
    writeln(output,' file ',fn,'  length=',length(indexed):1,
      '   maxlength=',maxlength(indexed):1)
  end {reportfile};

  procedure reportcomponent;
  begin
    writeln(output,'[0000]=',indexed^[0000]:4 oct,
		 '  [0001]=',indexed^[0001]:4 oct,
      '  [',maxword:6 oct,']=',indexed^[maxword]:6 oct)
  end {reportcomponent};

begin
  quit := false; getfn(indexed,fn);
  maxindex := 0 {only initialize new components};
  {first try to find an existing file by name given}
  reset(indexed); reportfile;
  {if file not found, length is zero; enter a new one}
  if length(indexed) = 0
    then begin rewrite(indexed); reportfile end
    else maxindex := maxlength(indexed);
  write(output,prompt);
  index := 0 {startup lastindex value};
  while (not quit) and (not eof(input)) do
    begin
      lastindex := index;
      if not eoln(input) then
	begin
	  read(input, ch);
	  if ch in ['R','r'] then
	    begin
	      read(input, index);
	      write(output,'old: ');
	      get(indexed,index);
	      reportcomponent
	    end
	  else if ch in ['W','w'] then
	    begin
	      read(input, index);
	      if index > maxindex then
		begin {new component}
		  write(output,'new: ');
		  maxindex := index;
		  indexed^[0] := index mod 10000b;
		  indexed^[1] := 1;
		  indexed^[maxword] := maxword mod 10000b;
		  reportcomponent;
		  put(indexed,index)
		end
	      else {previously defined}
		begin
		  write(output,'alt: ');
		  get(indexed,index);
		  reportcomponent;
		  put(indexed,index)
		end
	    end
	  else if ch in ['Q','q'] then quit := true
	  else if ch in ['L','l'] then reportfile
	  else writeln(output,'''',ch,'''<--??')
	end;
      if not quit then
	begin
	  write(output,prompt);
	  readln(input)
	end
    end
end.