My BIOS

.org 7C00h ; BIOS loading address

START:
    mov AX, 0 ; Clear register AX
    mov DS, AX ; Set DS to 0
    mov ES, AX ; Set ES to 0
    mov SI, 0 ; Reset starter index
    mov DI, 0 ; Reset usage index
    mov AH, 00h ; Reset keyboard
    int 16h ; Call BIOS to reset keyboard
    mov ah, 3Dh ; Open file
    mov al, 0 ; Access code to read
    mov dx, OFFSET file_name ; File name
    int 21h

    mov bx, ax ; Save file descryptor

CHECK_KEY:
    mov AH, 00h ; Get button
    int 16h ; Call BIOS to get button

    cmp AL, 53h ; Compare with Delete key code
    jne CHECK_KEY ; If Delete not pressed, re-run code
    jz read

    ; Run the following BIOS screen functions to print messages
    mov AH, 09h ; Print text on top screen
    mov DX, msg
    int 21h

    mov AH, 0
    int 16h ; Wait press button on keyboard
    cmp ah, 28h ; Run code if pressed button Escape or F10
    je quit ; Run if pressed ESC
    je save_exit ; Run if pressed F10

    jmp $ ; Infinite loop

quit:
    mov ah, 09h        ; Print text "Esc - Quit F10 - Save & Exit Setup" int bottom screen
    mov dx, quit_msg
    int 21h

    int 20h            ; Start operating system

    ; Your code to start operating system

save_exit:
    ; Open file
    mov eax, 5 ; System call to open file
    mov ebx, file_name ; Filename flag
    mov ecx, 0 ; Open file flag (O_CREAT | O_WRONLY)
    mov edx, 0644 ; File access permission
    int 0x80 ; Call system call

    ; Write data to file
    mov eax, 4 ; System call to write in file data
    mov ebx, eax ; File descryptor
    mov ecx, pc_health_status ; Write data of your pc status
    mov edx, pc_health_len ; Line length
    int 0x80 ; Call system call

    ; Close file
    mov eax, 6 ; System call to close file
    int 0x80 ; Call system call

    int 20h            ; Start operating system

    ; Your code to start operating system

read:
    mov ah, 3Fh ; Read from file
    mov bx, ax ; Get file descryptor
    lea dx, buffer ; Buffer to save data from file
    mov cx, 255 ; Count bytes to read (maximum 255)
    int 21h

    ; If reader value assign `null` close
    or ax, ax
    jz close_reader ; Close file call

    ; Write data to screen
    mov ah, 9 ; Print line to screen
    lea ds, buffer ; Get value from buffer
    int 21h

    jmp read ; Read next line

close_reader:
    mov ah, 3Eh ; Close file
    mov bx, ax ; Get file descryptor
    int 21h

section .data
    buffer db 1000 dup(0)
    file_name db "bios.ini", 0
    pc_health_status db "PCHealtStatus=Normal", 0
    pc_health_len equ $ - pc_health_status
    msg db "LMScript BIOS", 0
    quit_msg db "Esc - Quit F10 - Save & Exit Setup", 0

TIMES 510 - ($ - START) DB 0 ; Fill unused bytes with zeros

DW 0xAA55 ; End loading sector signature