操作系统学习笔记(7)--打印内存地址

文件的makefile中修改掉部分内容，我这里用到了前面的多余的东西。删除即可。

 

; This macro is used to calculate padding needed; to ensure that the boot sector is exactly 512 bytes; in size. The argument is the desired offset to be; padded to.%macro PadFromStart 1times (%1 - ($ - BeginText)) db 0%endmacro[BITS 16][ORG 0x07c00]BeginText: mov ax, 0 mov ds, ax mov es, ax mov dx, 0x15a4callPrintHexcallDispStr; 调用显示字符串例程.herejmp.here; 无限循环DispStr:movax, BootMessagemovbp, ax; ES:BP = 串地址movcx, 16; CX = 串长度movax, 01301h; AH = 13, AL = 01hmovbx, 000ch; 页号为0(BH = 0) 黑底红字(BL = 0Ch,高亮)movdl, 0int10h; 10h 号中断retPrintHex:pushamov cx, 4 ; 4 hex digits.PrintDigit:rol dx, 4 ; rotate so that lowest 4 bits are used mov ax, 0E0Fh; ah = request, al = mask for nybble and al, dl add al, 90h; convert al to ascii hex (four instructions) daa; I've spent 1 hour to understand how it works.. adc al, 40h daa int 10h loop .PrintDigitpopa retBootMessage:db"Hello, OS world!"PadFromStart 510Signature dw 0xAA55 ; BIOS controls this to ensure this is a boot sector

 

#targets : prerequisites# command# ...#kernel : floppy.bin objectfloppy.bin : bootsect.asmnasm bootsect.asm -o floppy.binobject : test.c test.hgcc -o object test.cclean :rm -f objectrm -f floppy.bin

 

使用bochs -f bochsrc.txt

运行时可以打印dx寄存器的内容15a4。

 

打印16进制算法设计的很巧妙。

 

下面的是打印新行的代码

; Print a newline.
PrintNL:   ; print CR and NL
 push ax
 mov ax, 0E0Dh ; CR
        int 10h
        mov al, 0Ah  ; LF
        int 10h
 pop ax
        ret