[BITS 16]        ;Tells the assembler that its a 16 bit code
[ORG 0x7C00]        ;Origin, tell the assembler that where the code will
                    ;be in memory after it is been loaded

CALL ClearScreen
MOV SI, setA20      ;Store string pointer to SI
CALL PrintString      ;Call print string procedure
JMP $                   ;Infinite loop

ClearScreen:
  XOR AL, AL        ;Set AL to 0
    MOV AH, 0x06      ;Function 06 of int 10h [scroll window up, if al = 0 clrscr]
    MOV CX, 0x00      ;Clear from 0,0
    MOV DX, 0x174f      ;To 23,79
    MOV BH, 0x00        ;Background color
    INT 0x10          ;Call video interrupt
RET

PrintCharacter:        ;Procedure to print character on screen
                    ;Assume that ASCII value is in register AL
    MOV AH, 0x0E        ;Function 0E of int 10h [print character]
    MOV BH, 0x00        ;Page no.
    MOV BL, 0x07        ;Text attribute 0x07 is lightgrey font on black background
    INT 0x10            ;Call video interrupt
RET                  

PrintString:          ;Procedure to print string on screen
                    ;Assume that string starting pointer is in register SI

next_character:        ;Lable to fetch next character from string
  MOV AL, [SI]        ;Get a byte from string and store in AL
  INC SI                ;Increment SI pointer
  OR AL, AL            ;Check if value in AL is zero (end of string)
  JZ exit_function  ;If AL equals 0 then LET'S GET OUT OF HERE!
  CALL PrintCharacter;Otherwise print the character in AL
  JMP next_character;Fetch next character from string

exit_function:        ;End label
RET                    ;Return from procedure

setA20 db 'Setting the A20 line..', 0

TIMES 510 - ($ - $$) db 0;Fill the rest of sector with 0, otherwise it won't boot
DW 0xAA55                      ;Add boot signature at the end of bootloader