INT 21,48 - Allocate Memory

	AH = 48h
	BX = number of memory paragraphs requested


	on return:
	AX = segment address of allocated memory block (MCB + 1para)
	   = error code if CF set  (see DOS ERROR CODES)
	BX = size in paras of the largest block of memory available
	     if CF set, and AX = 08 (Not Enough Mem)
	CF = 0 if successful
	   = 1 if error


	- returns segment address of allocated memory block AX:0000
	- each allocation requires a 16 byte overhead for the MCB
	- returns maximum block size available if error

	- see  INT 21,49,  INT 21,4A