1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
| mbrseg equ 7c0h ; boot sector address
outseg equ 800h ; store sector address
jmp start
megwelcome: db '------Wlecome Jiang Os------','$'
message1: db 'step1:now is in mbr','$'
message2: db 'step2:now jmp out mbr','$'
message3: db 'memory address is---','$'
message4: db 'CS:????','$'
start:
mov ax,mbrseg
mov ds,ax
call welcome
call newline
call newline
call inmbr
call showcs
call newline
call newline
jmp outseg:0 ;通过此条指令跳出MBR区
call outmbr
call showcs
welcome:
mov si,megwelcome
call printstr
ret
inmbr:
mov si,message1
call printstr
call newline
mov si,message3
call printstr
ret
outmbr:
mov si,message2
call printstr
call newline
mov si,message3
call printstr
ret
printstr: ;finish with '$'
mov al,[si] ; mov *si content to al
cmp al,'$' ; compare al to '$'
je disover ;
mov ah,0eh
int 10h
inc si
jmp printstr
disover:
ret
newline: ;显示回车换行
mov ah,0eh
mov al,0dh
int 10h
mov al,0ah
int 10h
ret
showcs: ;展示CS的值
mov ax,cs
mov dl,ah
call HL4BIT
mov dl, BH
call ASCII
mov [message4+3],dl
mov dl, Bl
call ASCII
mov [message4+4],dl
mov dl,al
call HL4BIT
mov dl, BH
call ASCII
mov [message4+5],dl
mov dl, Bl
call ASCII
mov [message4+6],dl
mov si, message4
call printstr
ret
;-----------------将16进制数字(1位)转换成ASCII码，输入DL,输出DL------
ASCII: CMP DL,9
JG LETTER ;DL>OAH
ADD DL,30H ;如果是数字,加30H即转换成ASCII码
RET
LETTER: ADD DL,37H ;如果是A～F,加37H即转换成ASCII码
RET
;-----------------取出1个字节Byte的高4位和低4位,输入DL,输出BH和BL----------
HL4BIT: MOV DH,dl
MOV BL,dl
SHR DH,1
SHR DH,1
SHR DH,1
SHR DH,1
MOV BH,DH ;取高4位
AND BL,0FH ;取低4位
RET
times 510-($-$$) db 0
db 0x55,0xaa
|