95 lines
2.5 KiB
NASM
95 lines
2.5 KiB
NASM
org 100h ;specify .COM file
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start:
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; mov al,13h ;AX=0000 at program start
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; int 10h ;init mode 13h
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; push word 0A000h ;Requires 80186 or higher to PUSH IMMED
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; pop es ;ES now points to mode 13h screen segment
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; push word 00000h ;
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; pop si
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mainloop:
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;This is where you do your mega-amazing tiny program.
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;Write 8-bit values to A000:0000 to draw some pixels.
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;Check for user wanting to leave by pressing ESC
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in al,60h ;read whatever is at keyboard port; looking for ESC which is #1
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cmp al,48h
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je upkey
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cmp al,4bh
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je leftkey
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cmp al,4dh
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je rightkey
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cmp al,50h
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je downkey
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cmp al,39h
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je space
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cmp al,38h
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je lalt
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mov dword [lastkeypressed], 0h ;Reset the current key as it is not one we are checking
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dec al ;if ESC, AL now 0
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jnz mainloop ;fall through if 0, jump otherwise
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mov al,03 ;AX=0000 due to mainloop exit condition
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int 10h ;Switch back to text mode as a convenience
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ret ;.COM files can exit with RET
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upkey:
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cmp ax, [lastkeypressed]
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je mainloop
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mov [lastkeypressed], ax
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mov ah,02
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mov dl,31h
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int 21h
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jmp mainloop
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leftkey:
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cmp ax, [lastkeypressed]
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je mainloop
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mov [lastkeypressed], ax
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mov ah,02
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mov dl,32h
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int 21h
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jmp mainloop
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rightkey:
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cmp ax, [lastkeypressed]
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je mainloop
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mov [lastkeypressed], ax
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mov ah,02
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mov dl,33h
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int 21h
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jmp mainloop
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downkey:
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cmp ax, [lastkeypressed]
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je mainloop
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mov [lastkeypressed], ax
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mov ah,02
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mov dl,34h
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int 21h
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jmp mainloop
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space:
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cmp ax, [lastkeypressed]
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je mainloop
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mov [lastkeypressed], ax
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mov ah,02
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mov dl,39h
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int 21h
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jmp mainloop
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lalt:
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cmp ax, [lastkeypressed]
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je mainloop
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mov [lastkeypressed], ax
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mov ah,02
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mov dl,38h
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int 21h
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jmp mainloop
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;Data segment
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lastkeypressed: db 0
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