汇编语言（二十二）之统计减去奇数的个数

输入一个正数，该数减去递增奇数（从1开始）直至小于等于零为止，计算该数减去奇数的个数

程序运行：

代码：

datas segment

     NUM      dw 17
	 ANS      dw 0
	
     NUM_string        db  0ffh, 0 ,100 dup(?)
	 inputNUM          db 'input NUM=$'
	 error_number    db 0dh,0ah,'error number$'
	 
	 outputANS         db 0dh,0ah,'ANS=$'
	 
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,inputNUM
	   mov ah,9
	   int 21h
	   ;输入a
	   lea dx,NUM_string
	   mov ah,10
	   int 21h
	   ;a转成十进制数
	   lea si,NUM_string+1
	   call translate_to_number
	   mov NUM,ax
	   
	   ;mov ax,NUM
       mov bx,1 
	   mov cx,0 
	   s:
	     sub ax,bx            ;减去奇数
		 inc cx 
		 add bx,2             ;奇数加2
		 cmp ax,0             ;判断ax是否大于0
		 jg s                  ;若大于0，循环继续
	  
       mov ANS,cx	  
		
       lea dx,outputANS           ;输出ANS
	   mov ah,9
	   int 21h
	   
	   mov ax,ANS
	   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