simple assembler program

boot.asm

[BITS 16]
[ORG 0x7C00]

; change video mode to 80x25
mov ah, 0x00
mov al, 0x03
int 0x10            ; call bios

; change boot backgrund color to blue
mov ah, 0x0B
mov bh, 0x00
mov bl, 0xF1
int 0x10            ; call bios

; print hello_world string
mov si, helloworldmessage 
call puthelloworld

; wait 'q' or ESC press button to exit
wait_key:
    mov ah, 0x00
    int 0x16        ; call bios
    cmp al, 'q'
    je shutdown
    cmp al, 0x1B
    je shutdown
    jmp wait_key

; shutdown function for shutdown :)
shutdown:
    mov ax, 0x5307  ; ACPI shutdown
    mov bx, 0x0001
    mov cx, 0x0003
    int 0x15        ; call bios function
    jmp $

; function for print hello world text
puthelloworld:
    mov ah, 0x0E    ; bios teletype
.next_char:
    lodsb
    cmp al, 0
    je .done
    int 0x10
    jmp .next_char
.done:
    ret

; hello world text
helloworldmessage db 'hi from asm, for quit press q or ESC :)', 0

; end of script
times 510-($-$$) db 0
dw 0xAA55           ; load sector