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BITS 16
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start:
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mov ax, 07C0h ; Set up 4K stack space after this bootloader
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add ax, 288 ; (4096 + 512) / 16 bytes per paragraph
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mov ss, ax
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mov sp, 4096
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mov ax, 07C0h ; Set data segment to where we're loaded
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add ax, 255
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mov ds, ax
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main_loop:
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call read_char ; Read character
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jmp main_loop ; Repeat
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read_char:
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mov ah, 0h ; Call Function "Read Char"
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int 16h ; Execute Keyboard Services
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mov ah, 0eh ; Call Function "Write char to TTY
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int 10h ; Execute Video Services
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cmp AL, 0x0d ; Insert new line, if keystroke was return
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je new_line
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ret
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new_line:
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mov AH, 03h ; Get Cursor position
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int 10h
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add DH, 1 ; Add 1 to cursor position
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mov AH, 02h ; Set Cursor to new position
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int 10h
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ret
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print_string: ; Routine: output string in SI to screen
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mov ah, 0Eh ; int 10h 'print char' function
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.repeat:
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lodsb ; Get character from string
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cmp al, 0
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je .done ; If char is zero, end of string
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int 10h ; Otherwise, print it
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jmp .repeat
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.done:
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ret
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times 510-($-$$) db 0 ; Pad remainder of boot sector with 0s
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dw 0xAA55 ; The standard PC boot signature
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