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16.1 描述了单元长度的标号
16.2 检测点 16.1
- 答案：
a[si]
word ptr b[0]
word ptr b[2]
2
16.3 检测点 16.2
- 答案：
mov ax, data
mov es, ax
16.4 直接定址表
16.5 实验 16
- 答案：
assume cs:code
code segment
start: mov ax, cs
mov ds, ax
mov si, offset screen
mov ax, 0
mov es, ax
mov di, 200h
mov cx, offset screenend - offset screen
cld
rep movsb
mov ax, 0
mov es, ax
mov word ptr es:[7ch * 4], 200h
mov word ptr es:[7ch * 4 + 2], 0
mov ax, 4c00h
int 21h
screen: jmp short set
;考虑到安装中断例程后偏移地址发生了变化，需要重新计算相关的偏移地址
table dw offset sub1 - offset screen + 200h, offset sub2 - offset screen + 200h, offset sub3 - offset screen + 200h, offset sub4 - offset screen + 200h
set: push bx
cmp ah, 3
ja sret
mov bl, ah
mov bh, 0
add bx, bx
;同上
call word ptr cs:(table - screen + 200h)[bx]
sret: pop bx
iret
sub1: push bx
push cx
push es
mov bx, 0b800h
mov es, bx
mov bx, 0
mov cx, 2000
sub1s: mov byte ptr es:[bx], ' '
add bx, 2
loop sub1s
pop es
pop cx
pop bx
ret
sub2: push bx
push cx
push es
mov bx, 0b800h
mov es, bx
mov bx, 1
mov cx, 2000
sub2s: and byte ptr es:[bx], 11111000B
or es:[bx], al
add bx, 2
loop sub2s
pop es
pop cx
pop bx
ret
sub3: push bx
push cx
push es
mov cl, 4
shl al, cl
mov bx, 0b800h
mov es, bx
mov bx, 1
mov cx, 2000
sub3s: and byte ptr es:[bx], 10001111B
or es:[bx], al
add bx, 2
loop sub3s
pop es
pop cx
pop bx
ret
sub4: push cx
push si
push di
push es
push ds
mov si, 0b800h
mov es, si
mov ds, si
mov si, 160
mov di, 0
cld
mov cx, 24
sub4s: push cx
mov cx, 160
rep movsb
pop cx
loop sub4s
mov cx, 80
mov si, 0
sub4s1: mov byte ptr [160*24+si], ' '
add si, 2
loop sub4s1
pop ds
pop es
pop di
pop si
pop cx
ret
screenend:
nop
code ends
end start
