INT 38 - PC-MOS/386 v3.0 - GET TASK CONTROL BLOCK
        AH = 04h
Return: ES = segment of Task Control Block (TCB) (see below)

Format of Task Control Block:
Offset  Size    Description
 00h  2 BYTEs   signature "HT"
 02h 23 BYTEs   ???
 19h    BYTE    task time slice
 1Ah  7 BYTEs   ???
 21h 11 BYTEs   name of currently executing task
 2Ch 79 BYTEs   ???
 7Bh  4 BYTEs   user name
 7Fh    BYTE    current output class
 80h  7 BYTEs   protection access rights, 2 bits per class (writeable!)
        ???