add documentation
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Tibo
parent
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1 changed files with 150 additions and 131 deletions
281
messages.asm
281
messages.asm
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@ -1,9 +1,11 @@
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org 0x7C00
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bits 16
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org 0x7C00 ; The boot code on a drive always gets loaded at address 0x7C00
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bits 16 ; .bin defaults to 16 bits
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WIDTH equ 0x50
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HEIGHT equ 0x18
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VIDEO_MODE equ 0x3
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;; FIXME: possible problem with HEIGHT being defined
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;; as one less than what VIDEO_MODE implies?
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WIDTH equ 0x50 ; 60
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HEIGHT equ 0x18 ; 24 (?)
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VIDEO_MODE equ 0x3 ; 80x25 screen, text mode
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;; see http://www.ctyme.com/intr/int-10.htm for interrupts
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@ -13,173 +15,190 @@ mov ax, VIDEO_MODE
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int 10h
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;; Clear screen
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mov ah, 0x06
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mov al, 0x00
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mov bh, 0x0F
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mov cx, 0x0000
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mov dh, HEIGHT
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mov dl, WIDTH
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mov ah, 0x06 ; scroll screen up
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mov al, 0x00 ; lines to scroll (0 = clear)
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mov bh, 0x0F ; bg/fg colour
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mov cx, 0x0000 ; upper row number, left col number (both 0)
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mov dh, HEIGHT ; lower row number (24)
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mov dl, WIDTH ; right col number (80)
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int 0x10
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;; Set cursor to bottom of screen
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mov dh, HEIGHT
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mov dl, 0x00
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mov bh, 0x00
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mov ah, 0x02
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mov ah, 0x02 ; set cursor position
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mov bh, 0x00 ; page number
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mov dh, HEIGHT ; row (bottommost row)
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mov dl, 0x00 ; col (leftmost col)
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int 0x10
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mov sp, 0x2000
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mov sp, 0x2000 ; initialise stack pointer
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.loop:
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;; Read character
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mov ah, 0x00
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int 0x16
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mov ah, 0x00 ; Read character
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int 0x16
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cmp al, 0x0d ; newline
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je .newline
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cmp al, 0x08 ; delete character
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je .change_color_mode
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cmp al, 0x1b ; escape character
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je .beep
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jmp .nonewline
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cmp al, 0x0d ; newline
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je .newline
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cmp al, 0x08 ; delete character
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je .change_color_mode
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cmp al, 0x1b ; escape character
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je .beep
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jmp .nonewline
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.change_color_mode:
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call .readbyte
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mov [color_mode], al
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jmp .loop
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call .readbyte
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mov [color_mode], al
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jmp .loop
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.newline:
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;; Scroll up window
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mov ah, 0x06
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mov al, 0x01
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mov bh, 0x0F
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mov cx, 0x0000
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mov dh, HEIGHT
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mov dl, WIDTH
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int 0x10
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;; Scroll up window
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mov ah, 0x06
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mov al, 0x01
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mov bh, 0x0F
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mov cx, 0x0000
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mov dh, HEIGHT
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mov dl, WIDTH
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int 0x10
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;; Get current cursor position
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mov bh, 0x00
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mov ah, 0x03
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int 0x10
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;; Get current cursor position
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mov bh, 0x00
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mov ah, 0x03
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int 0x10
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;; Move cursor to beginning of screen
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mov dl, 0x00
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mov ah, 0x02
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int 0x10
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;; Move cursor to beginning of screen
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mov dl, 0x00
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mov ah, 0x02
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int 0x10
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jmp .loop
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jmp .loop
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.beep:
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call .readduration
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mov ah, 0
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push ax
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mov al, 182 ; Prepare the speaker for the
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out 43h, al ; note.
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call .readbyte
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mov ah, 0
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sal ax, 5 ; multiply by 32
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add ax, 1140
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out 42h, al ; Output low byte.
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mov al, ah ; Output high byte.
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out 42h, al
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in al, 61h ; Turn on note (get value from
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; port 61h).
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or al, 00000011b ; Set bits 1 and 0.
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out 61h, al ; Send new value.
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;; mov bx, 50000 ; Pause for duration of note.
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pop bx
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push ax
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mov ax, 3125
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mul bx
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mov bx, ax
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pop ax
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call .readduration
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mov ah, 0
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push ax
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mov al, 182 ; Prepare the speaker for the
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out 43h, al ; note.
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call .readbyte
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mov ah, 0
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sal ax, 5 ; multiply by 32
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add ax, 1140
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out 42h, al ; Output low byte.
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mov al, ah ; Output high byte.
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out 42h, al
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in al, 61h ; Turn on note (get value from
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; port 61h).
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or al, 00000011b ; Set bits 1 and 0.
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out 61h, al ; Send new value.
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;; mov bx, 50000 ; Pause for duration of note.
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pop bx
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push ax
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mov ax, 3125
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mul bx
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mov bx, ax
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pop ax
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.pause1:
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mov cx, 65535
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mov cx, 65535
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.pause2:
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dec cx
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jne .pause2
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dec bx
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jne .pause1
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in al, 61h ; Turn off note (get value from
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; port 61h).
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and al, 11111100b ; Reset bits 1 and 0.
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out 61h, al ; Send new value.
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jmp .loop
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dec cx
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jne .pause2
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dec bx
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jne .pause1
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in al, 61h ; Turn off note (get value from
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; port 61h).
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and al, 11111100b ; Reset bits 1 and 0.
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out 61h, al ; Send new value.
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jmp .loop
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.nonewline:
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;; Write character
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;; Write character
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mov ah, 0x09
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mov bh, 0x00
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mov bl, [color_mode]
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mov cx, 0x01
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mov bh, 0x00
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mov bl, [color_mode]
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mov cx, 0x01
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int 0x10
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;; Get current cursor position
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mov ah, 0x03
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int 0x10
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;; Get current cursor position
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mov ah, 0x03
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int 0x10
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cmp dl, WIDTH
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jge .eol
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jmp .noeol
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cmp dl, WIDTH
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jge .eol
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jmp .noeol
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.eol:
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;; Scroll up window
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mov ah, 0x06
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mov al, 0x01
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mov bh, 0x0F
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mov cx, 0x0000
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mov dh, HEIGHT
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mov dl, WIDTH
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int 0x10
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;; Scroll up window
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mov ah, 0x06
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mov al, 0x01
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mov bh, 0x0F
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mov cx, 0x0000
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mov dh, HEIGHT
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mov dl, WIDTH
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int 0x10
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;; Move cursor to beginning of screen
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mov bh, 0
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mov dh, HEIGHT
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mov dl, 0x00
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mov ah, 0x02
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int 0x10
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jmp .loop
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;; Move cursor to beginning of screen
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mov bh, 0
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mov dh, HEIGHT
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mov dl, 0x00
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mov ah, 0x02
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int 0x10
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jmp .loop
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.noeol:
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;; Move cursor forward
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inc dl
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mov ah, 0x02
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int 0x10
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jmp .loop
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;; Move cursor forward
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inc dl
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mov ah, 0x02
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int 0x10
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jmp .loop
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;; Reads two characters from the keyboard buffer and converts them into a single byte
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;;
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;; The conversion happens as follows:
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;; ASCII 'a' is subtracted from each character (so 'a' = 0, 'b' = 1, ...)
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;; the first character is shifted left by 4
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;; the shifted and non-shifted values are then or'ed together to form a byte
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;;
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;; CLOBBERS
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;; - ax
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;; - bl
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.readbyte:
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;; Read character
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mov ah, 0x00
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int 0x16
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;; Read character is in al
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sub al, 'a'
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mov bl, al
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shl bl, 0x4
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mov ah, 0x00 ; Read character
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int 0x16
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;; Read character
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mov ah, 0x00
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int 0x16
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;; Read character is in al
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sub al, 'a'
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or al, bl
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ret
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;; Read character is in al
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sub al, 'a' ; Normalise
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mov bl, al
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shl bl, 0x4 ; First character is upper 4 bits
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mov ah, 0x00 ; Read character
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int 0x16
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;; Read character is in al
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sub al, 'a' ; Normalise
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or al, bl ; Combine both characters
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ret
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.readduration:
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;; Read duration (0-16 supported)
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mov ah, 0x00
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int 0x16
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;; Read character is in al
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sub al, 'a'
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ret
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;; Read duration (0-16 supported)
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mov ah, 0x00
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int 0x16
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;; Read character is in al
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sub al, 'a'
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ret
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halt: hlt
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color_mode: db 0x02
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;; Magic number must be in the last 2 bytes of the sector so
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;; fill the binary with zeroes until it is 510 bytes in size
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;; (magic number will use up the remaining 2)
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times 510 - ($ - $$) db 0
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dw 0xAA55
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dw 0xAA55 ;; Magic number to mark sector as bootable
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