8 Queen problem solver

program FPProgT15;

{$mode objfpc}{$H+}

uses
  {$IFDEF UNIX}{$IFDEF UseCThreads}
  cthreads,
  {$ENDIF}{$ENDIF}
  Classes,
  SysUtils;

type
  QueenArray = Array[1..8] of Integer;


var
  MainQueens: QueenArray;
  i: integer;
  {$R *.res}

function isLegit(Queens: QueenArray): Boolean;
var
   i, j: integer;
   final: boolean;
begin
     final := true;
     for i := 1 to 8 do
     begin
       if final = true then
       begin
         for j := i - 1 downto 1 do
         begin
            if Queens[i] = Queens[j] then final := false
            else if Queens[j] = Queens[i] - (i-j) then final := false
            else if Queens[j] = Queens[i] + (i-j) then final := false;
         end;
       end;
     if final = true then isLegit := true
     else isLegit := false;
     end;
end;

procedure quit;
begin
  writeln;
  writeln;
  writeln('Press <Enter> To Quit');
  readln;
end;

procedure DrawBoard(Queens: QueenArray);
var
   i, j: integer;
   isWhite: Boolean;
   OutStr: String;
begin
  for i := 8 downto 1 do
  begin
  OutStr := '';
    for j := 1 to 8 do
    begin
      if ((i + j) mod 2) = 0 then isWhite := false
      else isWhite := true;
      if Queens[j] = i then
      begin
        if isWhite = true then OutStr := OutStr + ' W Q'
        else OutStr := OutStr + ' B Q';
      end
      else
      begin
        if isWhite = true then OutStr := OutStr + ' WNQ'
        else OutStr := OutStr + ' BNQ'
      end;
    end;
    Writeln(OutStr);
  end;
  Writeln;
end;

procedure AdvanceQueen(Index: Integer);
var
  i: integer;
begin
  if MainQueens[Index] < 8 then MainQueens[Index] := MainQueens[Index] + 1 //if there is room to progress then progress
  else
  begin
    index := index + 1;
    for i := Index - 1 downto 1 do
    begin
      MainQueens[i] := 1
    end;
    if Index < 9 then AdvanceQueen(Index);
  end;
end;

begin
  for i := 1 to 8 do MainQueens[i] := 1; //initialise all the queens
  for i := 1 to 16777216 do
  begin
    AdvanceQueen(1);
    if isLegit(MainQueens) = true then
    begin
      DrawBoard(MainQueens);
      readln;
    end;
  end;
  quit;
end.