79 lines
2.0 KiB
NASM
79 lines
2.0 KiB
NASM
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;Y=100-60 cos((pi/180)*x)
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;Bit 7 6 5 4 3 2 1 0
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;Data R R R G G G B B
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.387
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.model small
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.stack 100
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.data
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msg db 10,13,'this is COS wave$'
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one_eighty dw 180
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scale dw 30
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hundred dw 100
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rint dw 0
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x dw 0
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.code
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main:
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mov ax,@data ; Initialize DS (needed for .exe-program)
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mov ds, ax
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mov ax, 0A000h ; Segment to video memory
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mov es, ax
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mov ax, 13h ;Standard video graphics mode
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int 10h ; switch to 320x200 mode
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mov cx,0
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l1:
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push cx ; store CX
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call get_cos
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mov bx, cx
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call vector_to_memory
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mov di, ax
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mov al, 03h ; color
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mov [es:di], al ; put pixel
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pop cx ; restore CX
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inc cx ; CX = CX + 1
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cmp cx, 320 ; right boarder reached?
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jne l1 ; no, next degree
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mov ah,09h ; display message
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lea dx,msg
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int 21h
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xor ah, ah
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int 16h ; keyboard (wait for key)
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mov ax, 3
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int 10h ; go to text mode
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mov ax, 4C00h
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int 21h ; return to DOS, exit code 0
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get_cos: ; Args: CX = angle (degree!)
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mov word[x],cx
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fldpi ; ST(0)=Pi, ST(1)=CX
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fimul word[x] ; ST(0)=Pi*CX
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fidiv word[one_eighty] ; ST(0)=(Pi*CX)/180(degree to rad)
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fcos ; ST(0)=sine (rad)
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fimul word[scale] ; ST(0)=sine*scale
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fild hundred
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fsub st,st(1) ;ST(0)=100-60*SIN((Pi*CX)/180)
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fist word [rint] ; store integer with rounding
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mov ax, word[rint] ; AX = Y
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ret ; Return: AX = Y (signed!)
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vector_to_memory: ; Calculate offset=Y*320+X
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;Args: BX = X, AX = Y
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push dx ; mul changes dx too
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mov cx, 320 ; video mode width
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mul cx ; DX:AX = AX * CX
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add ax, bx ; left indentation
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pop dx
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ret ; Return: AX = offset in memory
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end main
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