China DOS Union

When making a boot disk, the first part of autoexec.bat is:
@ECHO OFF
set EXPAND=YES
SET DIRCMD=/O:N
set LglDrv=27 * 26 Z 25 Y 24 X 23 W 22 V 21 U 20 T 19 S 18 R 17 Q 16 P 15
set LglDrv=%LglDrv% O 14 N 13 M 12 L 11 K 10 J 9 I 8 H 7 G 6 F 5 E 4 D 3 C
cls
call setramd.bat %LglDrv%
set temp=c:\
set tmp=c:\
path=%RAMD%:\;a:\;%CDROM%:\
copy command.com %RAMD%:\ > NUL
set comspec=%RAMD%:\command.com
copy extract.exe %RAMD%:\ > NUL
copy readme.txt %RAMD%:\ > NUL
But I don't know what expand=yes means. Hope some friend can point it out! Many thanks.

These are all lines from some old boot disks, and they're already outdated, so it doesn't matter if you leave them out.

Brother OP:
I'm puzzled by the same thing too.
If you ever get it figured out someday,
let little brother me know too.
My QQ number is:78302055