Int 21 Fn DF01  - Software Carousel - Switch To Another Task               [T]

   AX = DF01h
   BL = task number (00h = next task)

Return: AL = status
       00h Carousel not running
       01h successful
       FFh unsucessful
       AH = error code (01h,02h) (see below)

Values for error code:
 00h   invalid subfunction in AL
 01h   invalid task number
 02h   tried to switch to task with no memory size
 03h   tried to kill program in partition with no program running
 04h   tried to change size of an active memory partition
 05h   invalid memory size
 06h   tried to send command to task with a pending previous command