I think i started programming in assembly on PC around 1992. I learned a lot from my friend Edk. Who was a assembly wizard just like Sepp. Reverse engineering routines, writing emulators etc.
We made several demo’s like the one below. It must have been around 1994.
Just after this one, we started a demo which could run from a 5.25″ boot disk. No dos operating system.
When starting your pc, booting from a floppy you would get a starfield, with some text (from a bootsector) ,after that it would load the next sectors, wich contained the rest of the demo.
Due to directly programming soundcard and graphics card, this was hard to pull off on different kinds of hardware.
Demo gfx
Example of assembly code for a effect.
NAME plasma
.model small
.386
.data
colshades db +001h, 001h,+001h
db -001h,-001h,-000h
db +000h,-000h,-001h
db -000h,-000h,+000h
rgb_cols db 256*3 dup (?)
cosptr dw 0
sinptr dw 30
.code
demo proc near
show proc near
xor di,di
mov bp,200
show1:
mov cx,320
mov si,0
mov dx,0
show0:
; push ds
; mov ax,7000h
; mov ds,ax
; lodsb
; pop ds
call getsincos
add cosptr,1
stosb
loop show0
; add dx,1
add sinptr,1
dec bp
jnz show1
ret
show endp
effect proc near
; add cosptr,1
; add sinptr,0
ret
effect endp
getsincos proc near
push di
push ds
mov si,cosptr
mov di,sinptr
mov ax,7000h
mov ds,ax
lodsb ;get cos value
cmp si,320 ;einde costab?
jb cosok
xor si,si
lodsb
cosok:
mov ah,al
xchg si,di
lodsb ;get cos value
cmp si,320 ;einde costab?
jb sinok
xor si,si
lodsb
sinok:
xchg si,di
pop ds
mov cosptr,si
mov sinptr,di
mov dx,0
mov dl,al
add dl,ah
adc dh,0
shr dx,1
mov al,dl
; xor al,ah
; add al,ah
pop di
ret
getsincos endp
setcols proc near
push es
push ds
pop es
mov di,offset rgb_cols
mov si,offset colshades
mov dl,0 ;start with black
mov bh,0
mov bl,0
mov bp,4
set_rgball:
mov cx,64-1
set_rgb:
mov al,dl
stosb
mov al,bh
stosb
mov al,bl
stosb
mov al,[si]
add dl,al
mov al,[si+1]
add bh,al
mov al,[si+2]
add bl,al
loop set_rgb
add si,3
dec bp
jnz set_rgball
pop es
ret
setcols endp
setrgb proc near
mov dx,3c8h
xor al,al ;start with colour 00h
out dx,al
inc dx
mov si,offset rgb_cols
mov cx,256*3
rep outsb ;set 256 RGB values
ret
setrgb endp
wvtr proc near
mov dx,3dah
wtv:
in al,dx
test al,8
jz wtv
ret
wvtr endp
start:
cld
mov ax,@data
mov ds,ax
mov ax,0a000h
mov es,ax
mov ax,13h
int 10h ;screen 320x200 256 colours
call setcols
call setrgb
call show
mov al,11111101b
out 21h,al ;disable int
mloop:
call wvtr
; call show
call effect
mov ah,1
int 16h
jz mloop
xor ah,ah
int 16h
exit:
xor al,al
out 21h,al ;enable int
mov ax,3
int 10h ;screen 80x25 text
mov ax,4c00h
int 21h ;back to DOS
demo endp
end start
