Un-Advanced hacking FAQ

I see you have left-shift (shl) on the list, but what about right-shift? Is that a separate command (eg shr), or can shl take a negative second operand?

 

I think it's a seperate command, and it would just divide by 2^x, and no, shl doesn't take (maybe?) a negative second operand.

 

It would make sense that all operands are unsigned, I think... maybe...

 

dooay, couldja put this on the front page?
I refound it today (it's what I used to learn asm) and it's really really useful.

eh, bamp, sorry.
it's still a useful thread though.
^^

 

shr x,y -- divides x^y by two, rounding down. similar to shl

I think this is incorrect; you probably want "divides x by 2^y"

 

yes, that.
was it really the other way rounds?

 

Well, see for yourself.

 

hl x,y -- multiples x by 2^y, a lot faster than mul.
shr x,y -- divides x by 2^y, rounding down. similar to shl

*cough cough*

 

dooey must have edited it without posting that he did because my earlier quote was copy-pasted directly from the first post.

AHA!

Last edited by dooey100; October 27th, 2009 at 04:49 PM

i.e. today, after my post, before yours.

 

without even posting?
what a sly old meany.

thanks for putting the art of assembly up, btw.
real helpful for people who tend to lose their resources (moi)

 

without even posting?
what a sly old meany.

thanks for putting the art of assembly up, btw.
real helpful for people who tend to lose their resources (moi)

Midterm week.

Also, I be sneaky. Also, I interviewed for a job where I would be programming in assembly, which would be pretty cool. Then I could actually do stuff the way pros do it. (Because, well, technically, I would be a pro. )

 

aw, snap, that's awesome!
I wish you luck, pro.

 

umm.... right click what???

 

umm.... right click what???

My face melt from not understand. Please rephrase question to either:
A) Actually reference something on this page
B) Give context

 

umm.... right click what???

right click on desktop
mouse over "New"
click the "Folder" button
type in the name of your mod
press enter

you can now drag mod files here for distribution

feel free to put my name in the credits

 

srry for being unclear. I was asking what I right click when saving. The instructions are rather obscure about that part.

 

Jeeze, man...

And to save your awesome new hack: right click and choose Copy to Executable, then choose all modifications. A window with 4 options will appear, choose Copy All, and then the main window will minimize and a new window will appear, close the new window and you will be given the option to save.

You mean this?
Jeeze, you really need to be more specific, maybe quote the thing you're asking?
For where you right-click, just click on the code, anywhere inside the window for the EXE. Copy to Executable should be 4th from the bottom, and I'm pretty sure the rest of the directions are clear enough.
If that's not what you're asking for, then please QUOTE whatever your asking the question to, you're being rather obscure to us, yourself >.>;

 

Re: Jeeze, man...

yea thats what i meant... i'm srry for the unclarity...

 

Sorry for the bump, but I'm really stumped on this, and I've reached a point in the mod I'm normally working on where picture edits from cave story aren't enough to make this mod good, so I need to learn some assembly. I tried following the tutorial, but what I got doesn't seem to match what dooey said.

MOV EAX,[EBP+8]     ; this line is created for a process called pipelining that make the code run faster. Also because of this, [EAX+14], [ECX+14], and [EDX+14] will always be the same thing, as long as [EBP+8] is in EAX, ECX, or EDX. Any line that puts [EBP+8] in a register is doing this, and you can condense these to gain space if you need to (this is more advanced)
MOV ECX,[EAX+14]     ; this line takes the number that is in [EAX+14] and puts it in ECX so that we can do stuff with it. In a higher level language, [EAX+14] would be called a variable.
MOV EDX,[EBP+8]     ; pipelining
ADD ECX,[EDX+1C]     ; this line adds whatever is in [EDX+1C] to ECX (which currently contains [EAX+14] from before)
MOV EAX,[EBP+8]     ; pipelining
MOV [EAX+14],ECX     ; this takes whatever is in ECX and moves it back to [EAX+14]

So the overall result of the above code is to add [EDX+1C] to [EAX+14]. Lets try changing that to see exactly what [EDX+1C] and [EAX+14] are. Try changing the line ADD ECX,[EDX+1C] to ADD ECX,5 and play cave story and shoot the polar star to see what happens. You should find that when you shoot it, it will rise (independent of whether or not it is moving horizontally) This tells us that [EAX+14] is the current y-position of the bullet! And since [EAX+1C] is added to it every frame, then it must be the vertical velocity of the bullet!

I'm sure that I navigated to the right part of the program. It doesn't look exactly like the example but it has the parts it describles.

http://i144.photobucket.com/albums/r190/Vercci/1.png

Then I double clicked on the code and put this in

http://i144.photobucket.com/albums/r190/Vercci/2.png

I then got this (after pressing cancel) red text is scaring me.

http://i144.photobucket.com/albums/r190/Vercci/3.png

I then pressed the play button in ollydbg and went to a profile.dat that I made with the polar star ready. I fired it horizontally, but it actually fired normally, despite the tutorial saying that it should rise.

http://i144.photobucket.com/albums/r190/Vercci/4.png

I then tried firing it upward, and it doesn't move, dissappearing after what feels like the normal time for it to last.

http://i144.photobucket.com/albums/r190/Vercci/5.png


Am I doing something wrong? or is the tutorial wrong

 

Well there are a few things wrong here with this tutorial.

A) Adding 5 would not make the bullet go up, but rather down, since the y-axis in the cavestory system is inverted (positive is down, negative is up). It was made that way for the ease of rendering functions I believe.

2) 5 is an INCREDIBLY SMALL unit in cavestory. A pixel is actually 200 units (hexadecimal) so adding 5 would be like adding a hundredth of a pixel a frame. Try adding a number like 800, and don't worry if it eats the next line since the next line is actually pipelining.