Interrupt 21h
Function  48h   Allocate Memory 
		Allocates requested number of 16-byte paragraphs of memory 
entry   AH      48h 
        BX      number of 16-byte paragraphs desired 
return  CF      clear   AX      segment address of allocated space 
			BX      maximum number paragraphs available 
                set     AX      error code (7, 8) 
note    BX indicates maximum memory availible only if allocation fails