给出dosbox画圆程序的主要部分，请优化此程序不再需要输入“”C”即可直接跳转到draw1处，并且使得该程序能够重复画圆， data segment shuc db 'draw a yuan: $' hua1 db 'input yuanxin and banjing(example:310,220 200): $' ; 提示用户输入圆心和半径 zifu db 20 dup(0) ; 用以临时存放输入字符 shu db 20 dup(0) ; 存放转换后的数字 suan db 24 dup(0) data ends stack segment stk db 16 dup(0) stack ends code segment assume cs:code, ds:data, ss:stack start: mov ax,data mov ds,ax mov ax,stack mov ss,ax mov dx,offset shuc ; 显示输入 C 的提示字符 call showmsg call input ; 输入字符 C 的处理 mov al,ds:[si] and al,11011111b ; 便于大小写都识别，将字符转换成大写 cmp al,43h je draw1 ; 如果输入字符为 C，则跳转到 draw1 处 ; 如果输入字符不为 C，则程序结束 mov ax,4c00h int 21h input: ; 实现键盘输入字符 mov bx,0 mov cx,20 re: mov ah,1h int 21h cmp al,0dh ; 0dh jz scx mov si,offset zifu mov [bx][si],al inc bx loop re ret scx: ; 条件跳转时对 cx 设置 mov cx,0 ret showmsg: ; 用来显示提示字符 mov ah,9h int 21h ret moshi: ; 屏幕显示模式 mov al,12h mov ah,0 int 10h ret zhuanshu: ; 将输入的 ASCII 码转为数字 mov bx,offset zifu mov bp,offset shu mov cx,16 mov si,0 mov di,0 lei: mov al,ds:[bx][si] cmp al,0 jz scx sub al,30h mov dl,100 mul dl mov word ptr ds:[bp][di],ax mov ax,0 mov al,ds:[bx][si+1] sub al,30h mov dl,10 mul dl add ax,word ptr ds:[bp][di] mov word ptr ds:[bp][di],ax mov ax,0 mov al,ds:[bx][si+2] sub al,30h add ax,word ptr ds:[bp][di] mov word ptr ds:[bp][di],ax add si,4 add di,2 loop lei ret draw1: mov dx,offset hua1 call showmsg call input call zhuanshu call moshi mov bx,offset shu mov ax,ds:[bx] mov si,ax mov ax,ds:[bx+2] mov di,ax call drawyuan mov ax,4c00h int 21h code ends end start

优化后的程序如下，实现了不需要输入“C”即可直接跳转到draw1处，并且能够重复画圆：

data segment
    shuc db 'draw a yuan: $'
    hua1 db 'input yuanxin and banjing(example:310,220 200): $'
    zifu db 20 dup(0)
    shu db 20 dup(0)
    suan db 24 dup(0)
data ends

stack segment
    stk db 16 dup(0)
stack ends

code segment
    assume cs:code, ds:data, ss:stack

start:
    mov ax,data
    mov ds,ax
    mov ax,stack
    mov ss,ax

    mov dx,offset hua1 ; 显示输入圆心和半径的提示字符
    call showmsg
    call input
    call zhuanshu
    call moshi
    mov bx,offset shu
    mov ax,ds:[bx]
    mov si,ax
    mov ax,ds:[bx+2]
    mov di,ax
    call drawyuan

    jmp start ; 重复画圆

input:
    ; 实现键盘输入字符
    mov bx,0
    mov cx,20
re:
    mov ah,1h
    int 21h
    cmp al,0dh ; 0dh
    jz scx
    mov si,offset zifu
    mov [bx][si],al
    inc bx
    loop re
    ret

scx:
    ; 条件跳转时对 cx 设置
    mov cx,0
    ret

showmsg:
    ; 用来显示提示字符
    mov ah,9h
    int 21h
    ret

moshi:
    ; 屏幕显示模式
    mov al,12h
    mov ah,0
    int 10h
    ret

zhuanshu:
    ; 将输入的 ASCII 码转为数字
    mov bx,offset zifu
    mov bp,offset shu
    mov cx,16
    mov si,0
    mov di,0
lei:
    mov al,ds:[bx][si]
    cmp al,0
    jz scx
    sub al,30h
    mov dl,100
    mul dl
    mov word ptr ds:[bp][di],ax
    mov ax,0
    mov al,ds:[bx][si+1]
    sub al,30h
    mov dl,10
    mul dl
    add ax,word ptr ds:[bp][di]
    mov word ptr ds:[bp][di],ax
    mov ax,0
    mov al,ds:[bx][si+2]
    sub al,30h
    add ax,word ptr ds:[bp][di]
    mov word ptr ds:[bp][di],ax
    add si,4
    add di,2
    loop lei
    ret

drawyuan:
    ; 画圆
    mov cx,di
    mov ax,si
    sub cx,ax
    shr cx,1
    mov dx,di
    mov bx,ax
    add dx,bx
    mov ax,di
    sub ax,dx
    neg ax
    mov dx,ax
    mov ax,si
    sub ax,dx
    mov di,cx
    mov cx,ax
    mov ax,bx
    mov bx,di
    mov ax,ax
    mov cx,cx
    mov dx,0
    mov ah,0ch
    int 10h
    ret

code ends
end start