OS►30DayOS

Day2

Assembly language and Makefile

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; source of helloos.nas

org 0x7c00   ; these code should be loaded into memory 0x7c00

; FAT12 requirement code
jmp entry
db 0x90
...

; main program
entry:
	mov ax,0
	mov ss,ax
	mov sp,0x7c00
	mov ds,ax
	mov es,ax
	mov si,msg
putloop:
	mov al,[si]
	add si,1
	cmp al,0
	je fin
	mov ah,0x0e
	mov bx,15
	int 0x10     ; use bios to show one character
	jmp putloop
fin:
	hlt     ; put cpu into sleep, waiting for interrupt
	jmp fin
	
msg:
	db 0xa,0xa ; '\n', '\n'
	db "hello world"
	db 0xa
	db 0

Rebuild the IPL

Only the first 512 bytes is needed

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; source of ipl.nas
	ORG    0x7c00      

    JMP    entry
    DB    0x90
    DB    "HELLOIPL"    
    DW    512        
    DB    1        
    DW    1        
    DB    2        
    DW    224        
    DW    2880      
    DB    0xf0      
    DW    9        
    DW    18        
    DW    2        
    DD    0        
    DD    2880      
    DB    0,0,0x29    
    DD    0xffffffff    
    DB    "HELLO-OS   "  
    DB    "FAT12   "    
    RESB  18        

entry:
    MOV    AX,0      
    MOV    SS,AX
    MOV    SP,0x7c00
    MOV    DS,AX
    MOV    ES,AX

    MOV    SI,msg
putloop:
    MOV    AL,[SI]
    ADD    SI,1      
    CMP    AL,0
    JE    fin
    MOV    AH,0x0e      
    MOV    BX,15      
    INT    0x10      
    JMP    putloop
fin:
    HLT            
    JMP    fin        

msg:
    DB    0x0a, 0x0a    
    DB    "hello, world"
    DB    0x0a      
    DB    0

    RESB  0x7dfe-$    

    DB    0x55, 0xaa
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% nask.exe ipl.nas ipl.bin ipl.lst
% edimg.exe imgin:fdimg0at.tek wbinimg src:ipl.bin len:512 from:0 to:0 imgout:helloos.img
# equivlent to `qemu-img create` and `dd` under Unix-like system
% copy helloos.img qemu/fdimage0.bin
% make.exe -C qemu/

Makefile

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default:
	make.exe img

ipl.bin: ipl.nas
	nask.exe ipl.nas ipl.bin
	
helloos.img: ipl.bin
	dimg.exe imgin:fdimg0at.tek wbinimg src:ipl.bin len:512 from:0 to:0 imgout:helloos.img
	
asm:
	make.exe -r ipl.bin

img:
	make.exe -r helloos.img
	
run:
	make.exe img
	copy helloos.img qemu/fdimage0.bin
	make.exe -C qemu/

clean:
	del ipl.bin
	del helloos.img