画面上でアスタリスクを移動する必要があるこの小さなプログラムを作成しています。問題は、境界に到達するたびに余分なアスタリスクが表示されることです。その余分なアスタリスクを取り除く方法はありますか? 本当に簡単なプログラムです。
これまでの私のコードは次のとおりです。
.model small
.stack 256
.data
row db 10 ;Save the initial cursor coordinates in
col db 40 ;col and row.
msg1 db "*",'$' ;Asterisk to be used by the program.
msg2 db " ",'$'
mSetCursor macro ;Macro for placing the cursor in the screen.
;pre-conditions
;
; None
;
;post-conditions
;
; Asterisks will be printed on the screen,
; depending on the location of the cursor.
push ax
push bx
push dx
mov bh,0
mov ah,2
mov dh,row
mov dl,col
int 10h
pop dx
pop bx
pop ax
endm
.code
main proc
mov ax,@data
mov ds,ax
mov ax,03 ;Clean the screen.
int 10h
start:
mSetCursor ;Call the macro in charge of placing
;the asterisk on the screen.
mov ah,10h
int 16h
cmp ah,2dh ;Using the scan code of the letter X, we end
je exit ;the program once the "X" key is pressed.
cmp ah,0bh ;Using the scan code of the number 0, we clean
je clear ;the screen once the "0" key is pressed.
cmp ah,4bh ;Using the scan code of the left arrow,
je left ;we use the left arrow key to move the asterisk left.
cmp ah,48h ;Using the scan code of the up arrow,
je up ;we use the up arrow key to move the asterisk up.
cmp ah,4Dh ;Using the scan code of the right arrow,
je right ;we use the right arrow key to move the asterisk right.
cmp ah,50h ;Using the scan code of the down arrow,
je down ;we use the down arrow key to move the asterisk down.
mov ah,9 ;Code in charge of receiving the fifth message
mov dx, offset msg2 ;This code ensures that nothing happens while
int 21h ;keys that aren't arrow keys, 0, or X (quit) are pressed.
jmp start
left: ;We receive the asterisk, and decrease the value of col
mov ah,9 ;This starts the leftward movement of the asterisk.
mov dx, offset msg1 ;Finally, we skip to the Start label.
int 21h
dec col
cmp col,00 ;Disallow that the asterisk move past the
je right ;left side of the screen.
jmp start
right: ;Receive the asterisk, and increase the value of col.
mov ah,9 ;This starts the rightward movement of the asterisk.
mov dx, offset msg1 ;Finally, we skip to the Start label.
int 21h
inc col
cmp col,79 ;Disallow that the asterisk move past the
je left ;right side of the screen.
jmp start
down: ;We receive the asterisk and increase the value of row.
mov ah,9 ;This starts the downward movement of the asterisk.
mov dx, offset msg1 ;Finally, we jump to the Start label.
int 21h
inc row
cmp row,24 ;Disallow that the asterisk move past the
je up ;bottom of the screen.
jmp start
up: ;We receive the asterisk, and decrease the value of row.
mov ah,9 ;This starts the upward movement of the asterisk.
mov dx, offset msg1 ;Finally, we jump to the Start label.
int 21h
dec row
cmp row,-1 ;Disallow that the asterisk move past the
je down ;top of the screen.
jmp start
clear:
mov ax,03 ;Clean the screen.
int 10h
jmp start
exit: ;Label that lets us end the program.
mov ah,4ch
int 21h
main endp
end main