Question

以下代码应该添加两个一维矩阵并显示总和。当程序获取第二个矩阵的输入时出现问题：rd_next循环永远不会结束。然而，第一个矩阵的输入就好了。

data_seg segment
mat1 dw 3 dup(?)
mat2 dw 3 dup(?)
n db 3
ten dw 10
counter db ?
string db 10 dup(?)
msg1 db 10,13,"Enter first matrix: ","$"
msg2 db 10,13,"Enter second matrix: ","$"
msg3 db 10,13,"Enter a number: ","$"
data_seg ends

code_seg segment
assume cs:code_seg,ds:data_seg

print_string proc       
pop si      
pop dx
mov ah,9        
int 21h     
push si     
ret         
print_string endp

read_char   proc        
pop di  
mov ah,1        
int 21h     
mov ah,0
push ax     
push di     
ret
read_char endp

read_number proc
pop si      
mov bx,0    
mov dx,0

next_digit:
call read_char
pop ax          
cmp al,0Dh      
je  done
sub al,30h      
mov cl,al       
mov ch,0        
mov ax,bx       
mul ten      
add ax,cx   
mov bx,ax       
jmp next_digit  

done: push bx        
push si 
ret         
read_number endp

print_number proc       
pop si      
pop ax
mov bx,0        
mov dx,0
repeat1:        
mov cx,0        
mov dx,0        
div ten     
push dx     
inc counter     
cmp ax,0        
jne repeat1     

print_digit:
pop dx      
add dl,30h      
mov ah,2        
int 21h     
dec counter     
jnz print_digit 
push si     
ret         
print_number    endp

start:
mov ax,data_seg
mov ds,ax

mov al,n            
mov counter,al              ; initialize counter variable
mov bp,offset mat1          ; initialize pointer to first matrix

push offset msg1            ; prompt user to enter first matrix
call print_string

rd_next:
push offset msg3            ; prompt user for next number in matrix
call print_string        
call read_number            ; call the read_number procedure.
pop dx          
mov [bp],dx  
add bp,2        
dec counter
jnz rd_next                 ; loop back to read the next number.

mov counter,al              ; reset counter variable
mov bp,offset mat2          ; initialize pointer to second matrix

push offset msg2            ; prompt user to enter second matrix
call print_string
jmp rd_next

mov al,n
mov si,offset mat1
mov di,offset mat2

matrixsum:
mov bx,[si]
mov cx,[di]
add bx,cx
push bx
call print_number
inc si
inc di
dec al
jnz matrixsum

code_seg ends
end start

我没有看到代码有什么问题。我尝试创建一个单独的rd_next2循环来获取第二个矩阵的输入，但它不起作用。

Answer 1

哦，它会结束，只需要一些时间，因为你忘了重新初始化counter。将初始化代码移到rd_next内，例如：

    mov bp,offset mat1          ; initialize pointer to first matrix

    push offset msg1            ; prompt user to enter first matrix
    call print_string

rd_next:
    mov al,n            
    mov counter,al              ; initialize counter variable

学习使用调试器，这样您就可以单步执行代码，看看它为什么会这样做。

PS：你有一种巧妙的方法可以从函数中返回结果，但请不要这样做：D只需像其他人一样使用寄存器。

为什么rd_next代码在为第二个矩阵获取用户输入时永远不会结束？

1 个答案: