INT 2F U - DOS 3+ ASSIGN - GET DRIVE ASSIGNMENT TABLE
AX = 0601h
Return: ES = segment of ASSIGN work area and assignment table
Note:   under DOS 3+, the 26 bytes starting at ES:0103h specify which drive
each of A: to Z: is mapped to.  Initially set to 01h 02h 03h....

See also: 2F0600

2F0601 - DOS 3+ ASSIGN - GET DRIVE ASSIGNMENT TABLE