INT 21 - DOS 2+ - "MKDIR" - CREATE SUBDIRECTORY
AH = 39h
DS:DX -> ASCIZ pathname
Return: CF clear if successful
AX destroyed
CF set on error
AX = error code (03h,05h) (see AH=59h)
Notes:  all directories in the given path except the last must exist
fails if the parent directory is the root and is full
DOS 2.x-3.3 allow the creation of a directory sufficiently deep that
it is not possible to make that directory the current directory
because the path would exceed 64 characters
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=3Bh,AH=E2h/SF=0Ah,INT 2F/AX=1103h

See also: 213A

2139 - DOS 2+ - "MKDIR" - CREATE SUBDIRECTORY