135 lines
2.1 KiB
NASM
135 lines
2.1 KiB
NASM
org 0x7C00
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bits 16
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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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;; see http://www.ctyme.com/intr/int-10.htm for interrupts
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start:
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;; Use color mode
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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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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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int 0x10
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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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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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jmp .nonewline
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.change_color_mode:
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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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;; 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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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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;; 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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jmp .loop
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.nonewline:
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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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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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.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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;; 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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halt: hlt
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color_mode: db 0x02
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times 510 - ($ - $$) db 0
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dw 0xAA55
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