Int 21 Fn 58  - DOS 3+ - Get Or Set Memory Allocation Strategy             [D]

   AH = 58h
   AL = subfunction
       00h get allocation strategy

       Return: AX = current strategy
               00h low memory first fit
               01h low memory best fit
               02h low memory last fit
            ---DOS 5+ ---
               40h high memory first fit
               41h high memory best fit
               42h high memory last fit
               80h first fit, try high then low memory
               81h best fit, try high then low memory
               82h last fit, try high then low memory
       01h set allocation strategy
       BL = new allocation strategy (see above)
       BH = 00h (DOS 5+)

Return: CF clear if successful
   CF set on error
       AX = error code (01h) (see AH=59h)

Notes: the Set subfunction accepts any value in BL for DOS 3.x and 4.x;
     2 or greater means last fit
   the Get subfunction returns the last value set
   setting an allocation strategy involving high memory does not
     automatically link in the UMB memory chain; this must be done
     explicitly with AX=5803h in order to actually allocate high memory
   a program which changes the allocation strategy should restore it
     before terminating
   Toshiba MS-DOS 2.11 supports subfunctions 00h and 01h
   DR-DOS 3.41 reportedly reverses subfunctions 00h and 01h

See Also: AH=48h,AH=49h,AH=4Ah,INT 2F/AX=4310h,INT 67/AH=3Fh