Actually the statement made in the linked post is inaccurate. From RBI
list:
*************************************************************
INT 21 - MS-DOS 7.20 (Win98) - EXTENDED-LENGTH FILENAME OPERATIONS
AX = 43FFh
BP = 5053h ('PS')
CL = function
39h "mkdir" create directory
DS
X -> ASCIZ pathname
56h rename file
DS
X -> ASCIZ filename of existing file (no wildcards)
ES
I -> ASCIZ new filename (no wildcards)
Return: CF clear if successful
AX destroyed
CF set on error
AX = error code (03h,05h) (see #01680 at AH=59h/BX=0000h)
Note: these functions are equivalent to INT 21/AH=39h and INT 21/AH=56h,
but with a maximum path length of 128 characters instead of 67;
unlike INT 21/AX=71xxh, these functions are available under bare
DOS and not just in a Windows DOS box
SeeAlso: AH=39h,AH=56h,AX=7139h,AX=7156h
*************************************************************
Available to any programmer who would like to make a program LFN capable
under MSDOS7.20. No TSR's required!
HK