我的主引导记录代码：
;bit16 ; 16bit by default
org 0x7c00
jmp short start
nop
bsOEM db "OS423 v.0.1" ; OEM String
start:
;;cls
mov ah,06h ;Function 06h (scroll screen)
mov al,0 ;Scroll all lines
mov bh,0x0f ;Attribute (lightgreen on blue)
mov ch,0 ;Upper left row is zero
mov cl,0 ;Upper left column is zero
mov dh,24 ;Lower left row is 24
mov dl,79 ;Lower left column is 79
int 10h ;BIOS Interrupt 10h (video services)
;;print welcome msg
mov ah,13h ;Function 13h (display string), XT machine only
mov al,1 ;Write mode is zero: cursor stay after last char
mov bh,0 ;Use video page of zero
mov bl,0x0f ;Attribute (lightgreen on blue)
mov cx,mlen ;Character string length
mov dh,0 ;Position on row 0
mov dl,0 ;And column 0
lea bp,[msg] ;Load the offset address of string into BP, es:bp
;Same as mov bp, msg
int 10h
;;load sector into memory & 5678h:1234h
mov bx, 0x5678 ;segmented address
mov es, bx ;move segemented address to es
mov bx,0x1234 ;base address to bx
mov ah, 02 ;function read sectors
mov al, 01 ;# of sectors to load
mov ch, 00 ;track to read
mov cl, 02 ;sector to read
mov dh, 00 ;head to read
mov dl, 00 ;drive number
int 0x13 ;call interrupt 13
jmp 0x5678:0x1234 ;jump to memory address
int 20
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;variables;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
msg: db 'Welcome to Pradox OS 0.1! Authored by Jiansong he', 10, 13, '$'
mlen equ $-msg
padding times 510-($-$$) db 0 ;to make MBR 512 bytes
bootSig db 0x55, 0xaa ;signature (optional)
用于 nasm 编译并将二进制文件放入我的 .img 软盘的终端命令：
第1行：定义一个名为boot.img的软盘，块大小512字节，总共2880字节
line2：使用nasm编译器，将mbr.asm文件编译为二进制格式，将其存储在名为mbr.bin的文件中（这是我的主引导记录）
line3: 将 dt.asm 编译为二进制文件 dt.bin
line4: 将mbr.bin的内容放入boot.img中，块大小512，总共放入1块
line5: 将dt.bin的内容放入boot.img中，块大小512，位于物理扇区#2（逻辑扇区#1）
dd if=/dev/zero of=boot.img bs=512 count=2880
nasm -f bin mbr.asm -o mbr.bin
nasm -f bin dt.asm -o dt.bin
dd if=mbr.bin of=boot.img bs=512 count=1 conv=notrunc
dd if=dt.bin of=boot.img bs=512 seek=1 count=1 conv=notrunc
dt.asm 中的代码：
[BITS 16] ;Set code generation to 16 bit mode
ORG 0x5647:0x1234 ;set addressing to begin at 579b4H
startdt:
;call cls ;call routine to clear screen
;call dspmsg ;call routine to display message
call date
call cvtmo
call cvtday
call cvtcent
call cvtyear
call dspdate
call time
call cvthrs
call cvtmin
call cvtsec
call dsptime
int 20h ;halt operation (VERY IMPORTANT!!!)
cls:
mov ah,06h ;function 06h (Scroll Screen)
mov al,0 ;scroll all lines
mov bh,0x0f ;Attribute (bright white on blue)
mov ch,0 ;Upper left row is zero
mov cl,0 ;Upper left column is zero
mov dh,24 ;Lower left row is 24
mov dl,79 ;Lower left column is 79
int 10H ;BIOS Interrupt 10h (video services)
ret
dspmsg:
mov ah,13h ;function 13h (Display String)
mov al,1 ;Write mode is zero
mov bh,0 ;Use video page of zero
mov bl,0x0a ;Attribute (bright white on bright blue)
mov cx,mlen2 ;Character length
mov dh,0 ;position on row 0
mov dl,0 ;and column 0
lea bp,[welcom] ;load the offset address of string into BP
int 10H
ret
welcom: db 'jiansong Hes first Operating System :D',10,13,'$'
mlen2 equ $-welcom;
date:
;Get date from the system
mov ah,04h ;function 04h (get RTC date)
int 1Ah ;BIOS Interrupt 1Ah (Read Real Time Clock)
ret
;CH - Century
;CL - Year
;DH - Month
;DL - Day
cvtmo:
;Converts the system date from BCD to ASCII
mov bh,dh ;copy contents of month (dh) to bh
shr bh,1
shr bh,1
shr bh,1
shr bh,1
add bh,30h ;add 30h to convert to ascii
mov [dtfld],bh
mov bh,dh
and bh,0fh
add bh,30h
mov [dtfld + 1],bh
ret
cvtday:
mov bh,dl ;copy contents of day (dl) to bh
shr bh,1
shr bh,1
shr bh,1
shr bh,1
add bh,30h ;add 30h to convert to ascii
mov [dtfld + 3],bh
mov bh,dl
and bh,0fh
add bh,30h
mov [dtfld + 4],bh
ret
cvtcent:
mov bh,ch ;copy contents of century (ch) to bh
shr bh,1
shr bh,1
shr bh,1
shr bh,1
add bh,30h ;add 30h to convert to ascii
mov [dtfld + 6],bh
mov bh,ch
and bh,0fh
add bh,30h
mov [dtfld + 7],bh
ret
cvtyear:
mov bh,cl ;copy contents of year (cl) to bh
shr bh,1
shr bh,1
shr bh,1
shr bh,1
add bh,30h ;add 30h to convert to ascii
mov [dtfld + 8],bh
mov bh,cl
and bh,0fh
add bh,30h
mov [dtfld + 9],bh
ret
dtfld: db '00/00/0000'
dspdate:
;Display the system date
mov ah,13h ;function 13h (Display String)
mov al,0 ;Write mode is zero
mov bh,0 ;Use video page of zero
mov bl,0x0f ;Attribute
mov cx,10 ;Character string is 10 long
mov dh,4 ;position on row 4
mov dl,0 ;and column 28
push ds ;put ds register on stack
pop es ;pop it into es register
lea bp,[dtfld] ;load the offset address of string into BP
int 10H
ret
time:
;Get time from the system
mov ah,02h
int 1Ah
ret
;CH - Hours
;CL - Minutes
;DH - Seconds
cvthrs:
;Converts the system time from BCD to ASCII
mov bh,ch ;copy contents of hours (ch) to bh
shr bh,1
shr bh,1
shr bh,1
shr bh,1
add bh,30h ;add 30h to convert to ascii
mov [tmfld],bh
mov bh,ch
and bh,0fh
add bh,30h
mov [tmfld + 1],bh
ret
cvtmin:
mov bh,cl ;copy contents of minutes (cl) to bh
shr bh,1
shr bh,1
shr bh,1
shr bh,1
add bh,30h ;add 30h to convert to ascii
mov [tmfld + 3],bh
mov bh,cl
and bh,0fh
add bh,30h
mov [tmfld + 4],bh
ret
cvtsec:
mov bh,dh ;copy contents of seconds (dh) to bh
shr bh,1
shr bh,1
shr bh,1
shr bh,1
add bh,30h ;add 30h to convert to ascii
mov [tmfld + 6],bh
mov bh,dh
and bh,0fh
add bh,30h
mov [tmfld + 7],bh
ret
tmfld: db '00:00:00'
dsptime:
;Display the system time
mov ah,13h ;function 13h (Display String)
mov al,0 ;Write mode is zero
mov bh,0 ;Use video page of zero
mov bl,0x0f;Attribute
mov cx,8 ;Character string is 8 long
mov dh,5 ;position on row 5
mov dl,0;and column 0
push ds ;put ds register on stack
pop es ;pop it into es register
lea bp,[tmfld] ;load the offset address of string into BP
int 10H
ret
int 20H
我的测试环境是dosbox，我可以成功在屏幕上显示欢迎消息，但无法将另一个扇区加载到从0x5647:0x1234开始的内存中
谢谢
