删除屏幕上的字符

Question

我正在组装游戏,使用EMU8086进行学校项目.在这个游戏中,我需要允许用户输入一个字符串才能进步.当他输入字符串时,他可能会输入错误的内容并使用它backspace来纠正它.问题是backspace将光标移动到前一个字符上,但先前输入的字符仍然存在.为什么退格不清除前一个字符？如何修复程序,以便删除屏幕上的前一个字符？

我的代码是:

data segment

ends

stack segment
dw   128  dup(0)
ends    
StringHelper db 20 dup(?)
Line db 13,10,'$'
FullInput db 'You cant type more than 20 letters!!! please try again!!',13,10,'$'
t db '$'
code segment
PROC PrintMessage
  ;BX MUST have OFFSET OF MESSAGE
  ; if you want to go down a line do (lea bx,line)      
  mov dx,bx      
  mov ah,09h
  int 21h     
  ret 
 endp printMessage
 proc InputString          
;askes the user to input chars untill he press (enter) then puts it in StringHelper
b:
lea bx, StringHelper
mov cx,5  
xor dx,dx
a:                 ;restarts string helper
mov [bx],00
inc bx
loop a
lea bx, StringHelper
up:
cmp dx,20        ;cheacks if you wrote more than 20 chars
jz TryAgain
deleted:
xor ax,ax
mov ah,01h
int 21h
xor ah,ah
mov cx,08h        ;checks if the user inputed the backspace key
cmp al,cl
jz BackSpace
mov cx,0dh
cmp al, cl                ;checks if the user enters enter
jz InputIsOver
inc dx
mov [bx],al
inc bx
jmp up
TryAgain:
lea bx, line
call PrintMessage 
lea bx, FullInput
call PrintMessage
jmp b:
BackSpace:
cmp dx,0            ;checks if te user didnt just BackSpaced nothing
jz deleted
lea bx,stringhelper  ;gets the start of the array
add bx,dx            ;adds dx which is the indexer to how many chars  you     already wrote
mov [bx],00h         ;puts 0(nothing) at that place
dec bx
dec dx
jmp deleted          ;returen to get an extra input
InPutIsOver:

ret
endp
start:
  mov  ax, @data
 mov  ds, ax
mov al,13h
int 10h 
call InputString
 ; add your code here

mov ax, 4c00h
int 21h  

ends

end start

Answer 1

对于典型的屏幕和终端仿真器,打印退格字符只是将光标向左移动一个位置.要清除字符,请尝试打印退格键+空格+退格键.