;7_5.asm

bin_sub    macro  operand,count,result
           local  goon
           push   ax
           push   bx
           push   cx
           lea    bx,operand
           mov    al,[bx]
           mov    cx,count
           clc
goon:      sbb    al,[bx+1]
           inc    bx
           loop   goon
           mov    result,al
           pop    cx
           pop    bx
           pop    ax
           endm