[BITS 16]       ; We need 16-bit intructions for Real 
mode

[ORG 0x7C00]    ; The BIOS loads the boot sector into memory location 
0x7C00

reset_drive:

        mov ah, 0               ; RESET-command

        int 13h                 ; Call interrupt 13h

        or ah, ah               ; Check for error code

        jnz reset_drive         ; Try again if ah != 0

        ;vc에서 /base 10000 로 헀기 때문에 여기서부터 메모리를 로드
        ; 해야 한다. ES:BX 로 1000:0000h 이기 때문에 아래처럼 한다.

        mov ax, 1000h           ; es:bx <-- 1000:0000h 

        mov es, ax
        mov bx, 0h          ; Destination address = 0000:1000

        mov ah, 02h             ; READ SECTOR-command

        ; 두번째 섹터부터 3칸섹터가 커널이미지 섹터다.

        mov al, 3h             ; Number of sectors to read = 1

        mov ch, 0               ; Cylinder = 0

        ; 현재 첫번째섹터512 이며 두번째 섹터부터 3개 섹터가 커널이미지다

        mov cl, 02h             ; Sector = 2

        mov dh, 0               ; Head = 0

        int 13h                 ; Call interrupt 13h

        or ah, ah               ; Check for error code

        jnz reset_drive         ; Try again if ah != 0

A20Address:    ; Set A20 Address line here

    CLI

    CALL enableA20

    STI
    JMP Continue

enableA20:
        call enableA20o1

        jnz short enableA20done

        mov al,0d1h

        out 64h,al

        call enableA20o1

        jnz short enableA20done

        mov al,0dfh

        out 60h,al

enableA20o1:

        mov ecx,20000h

enableA20o1l:

        jmp short $+2

        in al,64h

        test al,2

        loopnz enableA20o1l

enableA20done:

        ret

Continue:   

        cli                 ; Disable interrupts, we want to be alone

        xor ax, ax

        mov ds, ax              ; Set DS-register to 0 - used by lgdt

        lgdt [gdt_desc]         ; Load the GDT descriptor

        mov eax, cr0            ; Copy the contents of CR0 into EAX

        or eax, 1               ; Set bit 0

        mov cr0, eax            ; Copy the contents of EAX into CR0

        jmp 08h:clear_pipe      ; Jump to code segment, offset clear_pipe

[BITS 32]                       ; We now need 32-bit instructions

clear_pipe:

        mov ax, 10h             ; Save data segment identifyer

        mov ds, ax              ; Move a valid data segment into the data segment register

        mov ss, ax              ; Move a valid data segment into the stack segment register

        mov esp, 090000h        ; Move the stack pointer to 090000h

        ; 10200h로 점프 200h는 vc로 링킹하면 기본 PE헤더(200h)를 붙여서 더했다.

        ; 10200h 즉 1000:0200h 로 점프

        ;jmp 1000:0200h

        jmp 10200h

        

gdt:                    ; Address for the GDT

gdt_null:               ; Null Segment

        dd 0

        dd 0

gdt_code:               ; Code segment, read/execute, nonconforming

        dw 0FFFFh

        dw 0

        db 0

        db 10011010b

        db 11001111b

        db 0

gdt_data:              ; Data segment, read/write, expand down

        dw 0FFFFh

        dw 0

        db 0

        db 10010010b

        db 11001111b

        db 0

gdt_end:		; Used to calculate the size of the GDT

gdt_desc:               ; The GDT descriptor

        dw gdt_end - gdt - 1    ; Limit (size)

        dd gdt                  ; Address of the GDT

times 510-($-$$) db 0           ; Fill up the file with zeros

        dw 0AA55h                ; Boot sector identifyer

#include 

int 
main(int argnr, char *args[])

{

  FILE 
*output, *input;

  int 
i, bytes_read, sectors_read, bytes_from_file;

  char 
buffer[512];

  if 
(argnr < 4) {

    printf("Invalid 
number of parameters.\n\n");

    printf("USAGE: 
%s [output] [input 1] [input 2] ... [input n]\n", args[0]);

    printf("Example: 
%s a.img bootsect.bin kernel.bin");

    exit(0);

  }

  output 
= fopen(args[1], "r");

// 
덮어 쓰기 할꺼냐고 물어보는 코든데 그냥 덮어쓰자. --

  if 
(output != NULL) {

    buffer[0] 
= 0;

  }

  fclose(output);

  output 
= fopen(args[1], "wb");

  for 
(i = 2; i < argnr; i++) {

    input 
= fopen(args[i], "rb");

    if 
(input == NULL) {

      printf("Missing 
input file %s. Aborting operation...", args[i]);

      fclose(output);

      exit(1);

    }

    bytes_read 
= 512;

    bytes_from_file 
= 0;

    sectors_read 
= 0;

    while(bytes_read 
== 512 && !feof(input)) {

      bytes_read 
= fread(buffer, 1, 512, input);

      if 
(bytes_read == 0)

        break;

      if 
(bytes_read != 512)

        memset(buffer+bytes_read, 
0, 512-bytes_read);

      sectors_read++;

      fwrite(buffer, 
1, 512, output);

      bytes_from_file 
+= bytes_read;

    }

    printf("%d 
sectors, %d bytes read from file %s...\n", sectors_read, bytes_from_file, 

args[i]);

    fclose(input);

  }

  fclose(output);

  return 
0;

}

// 
bro (bro@shinbiro.com)2004-02-17 - initial ( vc dev envronment setting )

// 
starting function

void 
start()

{   

    char* 
hello = "Hello OS!";

    unsigned 
char* vidmem = (unsigned char*)0xB8000;

    while( 
*hello != '\0' )        

    {

        *vidmem++ 
= *hello++;

        *vidmem++ 
= 7;        // 문자 기본 속성

    }   

    

    // 
커널이 끝나면 안된다. 계속 돌아야한다.   

    for(;;);

}