汇编语言（十六）之三数值求和

输入A、B、C三个数，如果存在一个数为0，则全部清零，否则求和输出

程序运行：

代码：

datas segment

      A    dw 1
	  B    dw 0
	  D    dw 3
	  S    dw 0
	  
	  a_string      db  0ffh, 0 ,100 dup(?)
	  b_string      db  0ffh, 0 ,100 dup(?)
      d_string      db  0ffh, 0 ,100 dup(?)	
	  
	 inputA          db 'input A=$'
	 inputB          db 0dh,0ah,'input B=$'
	 inputD          db 0dh,0ah,'input D=$'
     error_number    db 0dh,0ah,'error number$'
	 
	  outputA         db 0dh,0ah,'A=$'
	  outputB         db 0dh,0ah,'B=$'
	  outputD         db 0dh,0ah,'D=$'
	  outputS         db 0dh,0ah,'S=$'

datas ends

stacks segment stack

    db  100h dup(?)

stacks ends

codes segment

assume cs:codes,ds:datas,ss:stacks
main   proc  far
start:
       push ds
	   mov ax,0h
	   push ax
       mov ax,datas          ;初始化ds
	   mov ds,ax
       
	   ;输入a提示
	   lea dx,inputA
	   mov ah,9
	   int 21h
	   ;输入a
	   lea dx,a_string
	   mov ah,10
	   int 21h
	   ;a转成十进制数
	   lea si,a_string+1
	   call translate_to_number
	   mov A,ax
	   
	   ;输入b提示
	   lea dx,inputB
	   mov ah,9
	   int 21h
	   ;输入b
	   lea dx,b_string
	   mov ah,10
	   int 21h
	   ;b转成十进制数
	   lea si,b_string+1
	   call translate_to_number
	   mov B,ax
	   
	   ;输入d提示
	   lea dx,inputD
	   mov ah,9
	   int 21h
	   ;输入d
	   lea dx,d_string
	   mov ah,10
	   int 21h
	   ;d转成十进制数
	   lea si,d_string+1
	   call translate_to_number
	   mov D,ax
	   
	   mov ax,A
	   cmp ax,0          ;判断A是否为0
	   jz clear          ;若为0，则清零
	   mov bx,B
	   cmp bx,0          ;判断B是否为0
	   jz clear          ;若为0，则清零
	   mov dx,D
	   cmp dx,0          ;判断D是否为0
	   jz clear          ;若为0，则清零
	   
	   add ax,bx         ;求和
	   add ax,dx
	   
	   mov S,ax          ;把求和保存在S
	   jmp exit
	clear:
	   mov ax,0           ;清零
	   mov A,ax
       mov B,ax
       mov D,ax
       
	exit:
	   lea dx,outputA           ;输出A、B、D、S
	   mov ah,9
	   int 21h
	   
	   mov ax,A
	   call decimal
	   
	   lea dx,outputB
	   mov ah,9
	   int 21h
	   
	   mov ax,B
	   call decimal
	   
	   lea dx,outputD
	   mov ah,9
	   int 21h
	   
	   mov ax,D
	   call decimal
	   
	   lea dx,outputS
	   mov ah,9
	   int 21h
	   
	   mov ax,S
	   call decimal
       ret
	   
main endp

;字符串转换为十进制数
translate_to_number proc near 
   ;si:lenght first
   push cx 
   push dx 
   push bx 
   push si 
   push di 
   
   mov di,10
   mov ax,0
   mov cl,[si]
   mov ch,0 
   cmp cx,0 
   jz err
   inc si
   tran:
    mov bl,[si]
	inc si
    cmp bl,'0'
	jb err
	cmp bl,'9'
	ja err 
	sub bl,30h
    xor bh,bh	
	mul di 
	add ax,bx 
	loop tran
	jmp exit
	
err:
    lea dx,error_number
	mov ah,9
	int 21h 
	
	mov ax,4c00h
	int 21h
	
	exit:
	pop di 
	pop si 
	pop bx 
	pop dx
	pop cx 
	
	ret 
translate_to_number endp


decimal proc near
    
	 push ax
	 push cx
	 push dx
	 push bx
	 
	 cmp ax,0
	 jge plus
	 mov bx,ax
	 mov dl,'-'
	 mov ah,2
	 int 21h
	 neg bx
	 mov ax,bx
	 
	plus:
	 mov cx,0
	 mov bx,10
	de:
	 xor dx,dx
	 div bx
	 push dx
	 inc cx
	 cmp ax,0
	 jnz de
	 
	de1:
     pop dx
     add dl,30h
     mov ah,2 
     int 21h 
     loop de1 
    
	pop bx
	pop dx
	pop cx
	pop ax
	
	ret 
	
decimal endp
	 
codes ends

end main