So far I've learned some assembly, and i've tried using cmp and jz as a means of somewhat if statements. I just started learning so I don't know much complex stuff, but here is the code
The problem is, in my POLLING section, only The ESC does what it's supposed to do, close it. Any other key will do the same thing, draw a pixel up. So I'm guessing it's jumping straight to UP
Code:
;simple drawing program using bios and dos interrupts
;ASCII codes, using the numpad
;Up(8) 56
;Down(2) 50
;Left(4) 52
;Right(6) 54
;ESC 27
org 100h
INIT:
mov ah, 00 ;to set video mode
mov al, 13 ;graphics mode 320x200 256 color vga
int 10h ;change mode
mov bh, 00 ;change video mode
mov cx, 160 ;set x
mov dx, 100 ;set y -should be middle of screen..hopefully
POLLING:
mov ah, 08 ;to get input without echo, return stored in al
int 21h ;get the input
cmp al, 56 ;is the return value up?
jz UP ;if so jump to UP
cmp al, 50 ;is the return value down?
jz DOWN ;if so jump to DOWN
cmp al, 52 ;is the return value left?
jz LEFT ;if so jump to LEFT
cmp al, 54 ;is the return value right?
jz RIGHT ;if so jump to RIGHT
cmp al, 27 ;is the return value esc?
jz EXIT
UP:
dec dx ;decrement dx, the Y axis..The lower X is higher on the screen
jmp DRAW ;jump to DRAW ^^ at least i'm pretty sure it is.
DOWN:
inc dx ;increment dx, the Y axis
jmp DRAW
LEFT:
dec cx ;decrement cx, the X axis
jmp DRAW
RIGHT:
inc cx ;increment cx, the X axis
jmp DRAW
DRAW:
mov ah, 0ch ;for drawing pixel
mov al, 0Fh ;color
int 10h ;draw pixel. bh(page) cx, dx(axes) are already set
jmp POLLING ;go back to get more presses
EXIT:
mov ah, 00 ;to set video mode
mov al, 03 ;80x25 16 color text mode
int 10h ;return to video mode for dos
int 20h ;terminate
Originally Posted by Auxilium
So far I've learned some assembly, and i've tried using cmp and jz as a means of somewhat if statements. I just started learning so I don't know much complex stuff, but here is the code
The problem is, in my POLLING section, only The ESC does what it's supposed to do, close it. Any other key will do the same thing, draw a pixel up. So I'm guessing it's jumping straight to UP
When something doesn't work the first thing to assume is everything is wrong. Let's begin:
Code:
;simple drawing program using bios and dos interrupts
;ASCII codes, using the numpad
;Up(8) 56
;Down(2) 50
;Left(4) 52
;Right(6) 54
;ESC 27
org 100h
INIT:
mov ah, 00 ;to set video mode
mov al, 13 ;graphics mode 320x200 256 color vga
int 10h ;change mode
Will this do what you say? let's see...
nope. 13 =/= 13h what mode you set its actually...
Originally Posted by http://www.ctyme.com/intr/rb-0069.htm#Table10
since you are using a different mode with a 16 bit greyscale instead of 256 bit color its hard to predict what will happen, but lets continue...
EDIT: well i'd like to continue, but all my links are no longer in service so I will need some references to continue, since i don't know how to do this myself. But we need to figure this out next.
Code:
mov bh, 00 ;change video mode
mov cx, 160 ;set x
mov dx, 100 ;set y -should be middle of screen..hopefully
POLLING:
mov ah, 08 ;to get input without echo, return stored in al
int 21h ;get the input
The code after looks solid.
Code:
cmp al, 56 ;is the return value up?
jz UP ;if so jump to UP
cmp al, 50 ;is the return value down?
jz DOWN ;if so jump to DOWN
cmp al, 52 ;is the return value left?
jz LEFT ;if so jump to LEFT
cmp al, 54 ;is the return value right?
jz RIGHT ;if so jump to RIGHT
cmp al, 27 ;is the return value esc?
jz EXIT
UP:
dec dx ;decrement dx, the Y axis..The lower X is higher on the screen
jmp DRAW ;jump to DRAW ^^ at least i'm pretty sure it is.
DOWN:
inc dx ;increment dx, the Y axis
jmp DRAW
LEFT:
dec cx ;decrement cx, the X axis
jmp DRAW
RIGHT:
inc cx ;increment cx, the X axis
jmp DRAW
I'm unsure about this either.
Code:
DRAW:
mov ah, 0ch ;for drawing pixel
mov al, 0Fh ;color
int 10h ;draw pixel. bh(page) cx, dx(axes) are already set
jmp POLLING ;go back to get more presses
EXIT:
mov ah, 00 ;to set video mode
mov al, 03 ;80x25 16 color text mode
int 10h ;return to video mode for dos
int 20h ;terminate
Show me the resource you are using and we can work through this together.
Alright, thanks for the help.
/solved
I rewrote my code to use the WASD keys for movement, and it works now.
I'm guessing if you press any other key it will just go through the code till it reaches UP, then it will jump to drawing it.
I tried using the arrow keys, but I guess I got the codes wrong.
Here's my new code, everything works as planned, and exits successfully.
Code:
org 100h
START:
mov ah, 00 ;to set up the video mode
mov al, 13h ;320x200 256 Color VGA mode
mov bh, 00 ;video page
int 10h ;bios int to change video mode
AXIS:
mov cx, 160 ;X Axis
mov dx, 100 ;Y Axis
POLL:
mov ah, 08 ;to get keypress w/o echo
int 21h ;get press
;USING WASD FOR DIRECTION
cmp al, 119 ;UP
jz UP
cmp al, 115 ;DOWN
jz DOWN
cmp al, 97 ;LEFT
jz LEFT
cmp al, 100 ;RIGHT
jz RIGHT
cmp al, 27 ;ESC
jz ESC
UP:
dec dx ;make pixel go up
jmp PIXEL
DOWN:
inc dx ;make pixel go down
jmp PIXEL
LEFT:
dec cx ;make pixel go left
jmp PIXEL
RIGHT:
inc cx ;make pixel go right
jmp PIXEL
PIXEL:
mov ah, 0ch ;write pixel mode
mov al, 0Fh ;color, white
int 10h ;draw pixel, bh, dx, cx already set.
jmp POLL ;get another press
ESC:
mov ah, 00 ;same as in START
mov al, 03 ;80x25 16 color, normal mode for DOS
int 10h
int 20h ;terminate
Originally Posted by Auxilium
