Pascal/Turbo Pascal - dar sus anteriores primo

{Algo así}

program nprimos;

 uses

  crt;

  var

    n : array[1..255] of boolean;

    x, y : integer;

    num : integer;

   begin

     clrscr;

     write('entre numero : ');

     readln(num);

     writeln;

     for x := 1 to num do

     n[x] := true;

    for x := 2 to trunc(sqrt(num)) do

     begin

       y := sqr(x);

  repeat

    n[y] := false;

    inc(y,x);

   until y > num;

  end;

    for x := 1 to num do

    if n[x] then

    write(' ',x);

    readln;

  end.