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| ; bouncing ball
; masm 5.0
;***************************************************************
data_seg segment
count dw 1 ; count for a update deltatime
count_max equ 1
old_cs1c dw ?
old_ip1c dw ?
origin_x db ? ; cursor original size
origin_y db ?
v_x db 1 ; velocity of ball
v_y db 2 ;
stopped db 0 ; flag of stopped
ball_char equ '*' ; character represents ball
ball_attr equ 0eh ; attribute of ball
x_start equ 4 ; start position
y_start equ 3
x_min equ 1 ; defination of moving area : 0-----> y
x_max equ 20 ; |
y_min equ 1 ; \|
y_max equ 20 ; x
code_ctrl equ 1dh ; defination of key code
code_f equ 21h
code_x equ 2dh
bit_ctrl equ 04h
data_seg ends
;***************************************************************
stack_seg segment stack ; can't omit 'stack'
dw 100 dup(?)
tos label word
stack_seg ends
;***************************************************************
code_seg segment
;--------------------
main proc far
assume cs: code_seg, ss: stack_seg, ds: data_seg, es:data_seg
start:
;setup ss and sp
mov ax, stack_seg
mov ss, ax
mov sp, offset tos
;setup stack for return
;push ds
;sub ax, ax
;push ax
;setup ds and es
mov ax, data_seg
mov ds, ax
mov es, ax
;main code
; save old timer interrupt vector
mov al, 1ch
mov ah, 35h
int 21h
mov old_cs1c, es
mov old_ip1c, bx
push ds
; set new timer interrupt vector
mov dx, offset update
mov ax, seg update
mov ds, ax
mov al, 1ch
mov ah, 25h
int 21h
pop ds
; enable timer and keyboard interrupt
in al, 21h
and al, 11111100b
out 21h, al
sti
; clear screen
call clear_scr
; save cursor original size
mov bh, 0
mov ah, 3
int 10h
mov origin_y, ch
mov origin_x, cl
; hide cursor
mov cx, 80h
mov ah, 1
int 10h
; set cursor position
mov bh, 0
mov dh, x_min - 1 ; row and column
mov dl, y_min - 1
mov ah, 2
int 10h
; draw moving area
mov al, '=' ; character
mov bh, 0 ; page
mov bl, 0dah
mov cx, y_max - y_min + 3
mov ah, 9
int 10h
; set cursor position
mov bh, 0
mov dh, x_max + 1 ; row and column
mov dl, y_min - 1
mov ah, 2
int 10h
; draw moving area
mov al, '=' ; character
mov bh, 0 ; page
mov bl, 0dah
mov cx, y_max - y_min + 3
mov ah, 9
int 10h
; set start position
mov bh, 0
mov dh, x_start ; row and column
mov dl, y_start
mov ah, 2
int 10h
main_loop:
get_ctrl_f:
; get keyboard status
mov ah, 2
int 16h
test al, bit_ctrl ; if pressed ctrl
jz main_loop
; is any key pressed
mov ah, 0bh
int 21h
inc al
jnz main_loop
; get another key
mov ah, 0
int 16h
cmp ah, code_x ; if pressed x => exit
je exit
cmp ah, code_f ; if pressed f => toggle stop
jne main_loop
mov al, 1
xor stopped, al
jmp main_loop
exit:
call clear_scr
; restore old timer interrupt vector
mov dx, old_ip1c
mov ds, old_cs1c
mov al, 1ch
mov ah, 25h
int 21h
; reset cursor
mov ch, origin_y
mov cl, origin_x
mov ah, 1
int 10h
; return
mov ax, 4c00h
int 21h
main endp
;--------------------
update proc near
; frame update
push ds
push ax
push bx
push cx
push dx
mov ax, data_seg
mov ds, ax
sti
cmp stopped, 1
je update_exit
dec count
jnz update_exit
mov count, count_max ; update interval
; clear previous position
mov al, ' '
mov bh, 0 ; page
mov bl, 0 ; attribute
mov cx, 1 ; repeat times
mov ah, 9 ; show char
int 10h
; get current position dh, dl
mov bh, 0 ; page
mov ah, 3 ; get cursor position
int 10h
; calculate next position
cmp dh, x_min
ja no_min_x
neg v_x
no_min_x:
cmp dh, x_max
jb add_x
neg v_x
add_x:
add dh, v_x
cmp dl, y_min
ja no_min_y
neg v_y
no_min_y:
cmp dl, y_max
jb add_y
neg v_y
add_y:
add dl, v_y
; set new cursor position
mov bh, 0
mov ah, 2
int 10h
; show ball
mov al, ball_char
mov bh, 0 ; page
mov bl, ball_attr ; attribute
mov cx, 1 ; repeat times
mov ah, 9 ; show character
int 10h
update_exit:
cli
pop dx
pop cx
pop bx
pop ax
pop ds
iret
update endp
;--------------------
clear_scr proc near
; clear screen
push ax
push bx
push cx
push dx
mov ah, 6 ; scroll up screen
mov al, 0 ; blank screen
mov bh, 7 ; blank line
mov ch, 0 ; upper left row
mov cl, 0 ; upper left column
mov dh, 24 ; lower right row
mov dl, 79 ; lower right column
int 10h
; locate cursor to upper left
mov bh, 0 ; page
mov dx, 0 ; row and column
mov ah, 2 ; locate cursor
int 10h
pop dx
pop cx
pop bx
pop ax
ret
clear_scr endp
;--------------------
code_seg ends
;***************************************************************
end start
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