Ms-Dos - interrupcion Ms-Dos

Alguien sabe como se acceder a un directorio cualquiera a traves de los servicios de interrupcion del Ms-Dos,osea cual interrupcion se usa y que cargar en los registros de proposito general

esto dice en la listas de Ralph Brown

_____________D-213B_______________________________
INT 21 - DOS 2+ - "CHDIR" - SET CURRENT DIRECTORY
AH = 3Bh
DS:DX -> ASCIZ pathname to become current directory (max 64 bytes)
Return: CF clear if successful
AX destroyed
CF set on error
AX = error code (03h) (see AH=59h)
Notes: if new directory name includes a drive letter, the default drive is
not changed, only the current directory on that drive
changing the current directory also changes the directory in which
FCB file calls operate
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=47h,INT 2F/AX=1105h