The following unit demonstrates scanning a folder for directories and subdirectories and storing the results in a binary tree structure.

http://www.awitness.org/delphi_pascal_tutorial/index.html

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls, FileCtrl;

type
  link=^node;
  node=record filename:string;  l, r:link end;  {tree node to store directories}
  TForm1 = class(TForm)
    FileSearch: TButton;
    TreePrint: TButton;
    procedure FormCreate(Sender: TObject);
    procedure FileSearchClick(Sender: TObject);
    function FileLook(Filespec:string):boolean;
    Function TreeInsert(Fname:string; q:link):link;
    procedure TreePrintClick(Sender: TObject);
    Procedure PrintTree(q:link);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;
  t, head, z: link;
  fs:textfile; {*********************************}
  flcount:integer;
implementation

{$R *.DFM}

procedure TForm1.FormCreate(Sender: TObject);
begin
new(z); new(head);  {initialize binary tree head}
head^.filename:=''; head^.r:=z;  head^.l:=z;  {set key to nothing, lowest value on sorted tree}
						{z is a dummy node, similar to setting to 'nil'}
     flcount:=0;  {count the number of folders during the print routine}
end;

procedure TForm1.FileSearchClick(Sender: TObject);
var
found:boolean;
begin
Found:=FileLook('c:\windows\*.*'); {**************scan this folder for sub dirs}
If found then MessageDlg('DUN!', mtInformation, [mbOk], 0)
   else MessageDlg('Directory does not exist', mtError, [mbOk], 0);
end;


Function TForm1.FileLook(Filespec:string):boolean; {scan for subdirs code}
var
  x:link; {tree link, only needed if you had additional fields in the record to fill}
  validres:integer; {SearchRec routines return 0 if successful}
  SearchRec  : TSearchRec;
  DirPath, DirName, Flname : string; {search for subdirs flname will be *.*}
begin

     DirPath:=ExtractFilePath(FileSpec);
     Result:= DirectoryExists(DirPath);
     If not Result then exit; {some error checking code}
     Flname:=ExtractFileName(FileSpec); {save the wild cards in the filespec}
     validres := FindFirst(FileSpec, faDirectory, SearchRec);
     while validres=0 do begin
          If (SearchRec.Attr and faDirectory>0) and (SearchRec.Name[1]<>'.') then   begin

		{ignore the two dotted directories, do an and on the attributes to confirm 
		that the current searchrec is a directory}

              dirname:=SearchRec.Name; {extract the directory name}
              x:=TreeInsert(dirpath + dirname, head); {add the dirname to the current path
							and insert onto tree}
              FileLook(Dirpath+ dirname + '\' + Flname); {now check this new dir for subdirs
							using a recursive call to the function}
          end;
          validres:=FindNext(SearchRec);  {if it was not a directory or function returned 
					   from recursive search for subdirectories keep looking 
						in current path}
     end;
end;

Function TForm1.TreeInsert(Fname:string; q:link):link;
var st:link;  {st - the previous link, search until insertion value is less than current tree val}
begin
repeat
      st:=q;
      if fname<q^.filename then q:=q^.l else q:=q^.r;
until q=z;  {dummy node indicates search end, similar to nil pointer, easier to code}
new(q); q^.filename:=fname;  {create a new leaf node, insert value}
q^.l:=z; q^.r:=z;  {set leaf node pointers to dummy value}
if fname<st^.filename then st^.l:=q else st^.r:=q;  {use st to attach leaf to tree}
Result:=q;  {result only needed if you had additional record fields to fill in}
end;

procedure TForm1.TreePrintClick(Sender: TObject);
begin
assignfile(fs, 'c:\treeprint.txt');  {******************}
rewrite(fs);
PrintTree(head);  {pass the head pointer of the tree}
CloseFile(fs);
MessageDlg('TREE DUN!', mtInformation, [mbOk], 0);
end;

Procedure Tform1.PrintTree(q:link);  
{recursively search tree to left (less than) nodes and then search to the right (greater than nodes) to get an alphabetically sorted printout to file}
begin
     if q<>z then begin
        PrintTree(q^.l);
        Writeln(fs, inttostr(flcount) + ' : ' + q^.filename);  
	flcount:=flcount+1;  {compare count to property menu directory count}
        PrintTree(q^.r);
     end;
end;

end.