246 lines
5.1 KiB
NASM
Executable File
246 lines
5.1 KiB
NASM
Executable File
[BITS 16]
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[ORG 0x7C00]
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section .text
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start:
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jmp near Boot
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Disk_ID db "COS2000A" ;Fabricant + n° de série Formatage
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Sectors_Size dw 512 ;Nombre d'octets/secteur
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Sectors_Per_Cluster db 1 ;Nombre de secteurs/cluster
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Reserved_Sectors dw 1 ;Nombre de secteurs réservé
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Fats_Number db 2 ;Nombre de copies de la FAT
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Fits_Number dw 224 ;Taille du répertoire racine
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Sectors_Per_Disk dw 2880 ;Nombre secteurs du volume si < 32 Mo
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Media_Descriptor db 0xF0 ;Descripteur de média
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Sectors_Per_Fat dw 9 ;Nombre secteurs/FAT
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Sectors_Per_Track dw 18 ;Nombre secteurs/piste
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Heads_Number dw 2 ;Nombre de tete de lecture/écriture
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Sectors_Hidden dd 0 ;Nombre de secteurs cachés
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Sectors_Per_Disk2 dd 0 ;Nombre secteurs du volume si > 32 Mo
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Boot_Drive db 0 ;Lecteur de démarrage
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Reserved db 0 ;NA (pour NT seulement)
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Extended_Boot_ID db 0x29 ;Signature Boot étendu 29h
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Serial_Number dd 0x01020304 ;N° de série
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Disk_Name db "COS2000 " ;Nom de volume
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Fat_Type db "FAT12 " ;Type de système de fichiers
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Boot_Message db "Cos2000",0
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Entre_Message db "Fichier",0
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Loading_Message db "Charger",0
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System_File db "Al",0,"o",0,"a",0,"d",0,"e",0,0x0F,0,0x38,"r",0,".",0,"s",0,"y",0,"s",0,0,0,0,0,0xFF,0xFF,0xFF,0xFF
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Is_Ok db " [ OK ]",0x0A,0x0D,0
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Is_Failed db " [ERREUR]",0x0A,0x0D,0
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The_Dot db '.',0
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Boot_Error:
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mov si,Is_Failed
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call ShowString
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xor ax,ax
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int 0x16
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int 0x19
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Boot_Ok:
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mov si,Is_Ok
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call ShowString
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ret
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Boot:
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push cs
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push cs
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pop es
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pop ds
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mov [Boot_Drive],dl
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cli
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mov ax,0x9000
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mov ss,ax
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mov sp,0xFFFF
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sti
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mov si,Boot_Message
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call ShowString
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xor ax,ax
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int 0x13
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jc Boot_Error
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mov cx,[Reserved_Sectors]
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add cx,[Sectors_Hidden]
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adc cx,[Sectors_Hidden+2]
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mov bx,[Sectors_Per_Fat]
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mov di,Fat_Buffer
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push bx
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push cx
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readfat:
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call ReadSector
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jc Boot_Error
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inc cx
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add di,[Sectors_Size]
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dec bx
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jnz readfat
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pop cx
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pop bx
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xor ax,ax
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mov al,[Fats_Number]
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mul bx
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add cx,ax
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mov ax,32
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mul word [Fits_Number]
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div word [Sectors_Size]
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add ax,cx
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sub ax,2
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mov word [Serial_Number],ax
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xor dx,dx
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call Boot_Ok
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mov si,Loading_Message
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call ShowString
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Find_System:
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mov di,Buffer
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call ReadSector
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jc Near Boot_Error
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xor bx,bx
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Next_Root_Entrie:
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cmp byte [di],0
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je near Boot_Error
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push di
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push cx
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mov si,System_File
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mov cx,32
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rep cmpsb
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pop cx
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pop di
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je System_Found
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add di,32
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add bx,32
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inc dx
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cmp dx,[Fits_Number]
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ja near Boot_Error
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cmp bx,[Sectors_Size]
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jb Next_Root_Entrie
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inc cx
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jmp Find_System
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System_Found:
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call Boot_Ok
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mov si,Entre_Message
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call ShowString
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mov cx,[di+26+32]
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mov ax,0x0080
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mov es,ax
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push es
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mov di,0x0
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push di
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mov si,The_Dot
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Resume_Loading:
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cmp cx,0x0FF0
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jae Finish_Loading
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push cx
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add cx,word [Serial_Number]
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call ReadSector
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pop cx
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jc near Boot_Error
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call ShowString
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add di,[Sectors_Size]
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call NextFatGroup
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jc near Boot_Error
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jmp Resume_Loading
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Finish_Loading:
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call Boot_Ok
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retf
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;====================READSECTOR=======================
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;Lit le secteur logique LBA CX et le met en es:di
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;-> CX (limité à 65536 secteurs, soit 32 Mo avec secteur 512 octets)
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;<- Flag Carry si erreur
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;=====================================================
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ReadSector:
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pusha
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mov ax,cx
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xor dx,dx
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div word [Sectors_Per_Track]
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inc dl
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mov bl,dl
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xor dx,dx
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div word [Heads_Number]
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mov dh, [Boot_Drive]
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xchg dl,dh
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mov cx,ax
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xchg cl,ch
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shl cl,6
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or cl, bl
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mov bx,di
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mov si, 4
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mov al, 1
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Read_Again:
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mov ah, 2
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int 0x13
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jnc Read_Done
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dec si
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jnz Read_Again
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Read_Done:
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popa
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ret
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;===================NEXTFATGROUP======================
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;Renvoie en CX le groupe qui succède dans la FAT le groupe CX
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;-> CX
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;<-
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;=====================================================
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NextFatGroup:
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push bx
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push dx
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push di
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mov ax,cx
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mov bx,ax
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and bx,0000000000000001b
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shr ax,1
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mov cx,3
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mul cx
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mov di,Fat_Buffer
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add di,ax
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cmp bx,0
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jnz Even_Group
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Odd_Group:
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mov dx,[di]
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and dx,0x0FFF
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mov cx,dx
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jmp Next_Group_Found
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Even_Group:
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mov dx,[di+1]
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and dx,0xFFF0
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shr dx,4
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mov cx,dx
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Next_Group_Found:
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pop di
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pop dx
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pop bx
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ret
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;======================SHOWSTR========================
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;Affiche la chaine de caractère pointé par ds:si à l'écran
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;-> DS, SI
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;<- Flag Carry si erreur
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;=====================================================
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ShowString:
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pusha
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Next_Char:
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lodsb
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or al,al
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jz End_Show
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mov ah,0x0E
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mov bx,0x07
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int 0x10
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jmp Next_Char
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End_Show:
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popa
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ret
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times 510-($-$$) db ' '
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dw 0xAA55
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Buffer equ $
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Fat_Buffer equ $+512
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section .bss
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;Buffer resb 512
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;Fat_Buffer resb 10000
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