Cheat Engine

[Dr.Disrespect]

Hi there. I have some questions(sorry for my English):
1. If I call "rand", what is the range of the random number? Is it from 0 - 65535 or something? Moreover, can i define the range?

2. Please take a look at the following code:

[Zanzer]

OR performs a bitwise or.
In essence, it sets EAX equal to 1 or 0 depending on whether or not the first bit inside EAX already equals 1 or 0.
RAND returns several possible values. However, those values must either be even or odd.
The OR basically determines if the returned value is odd (1) or even (0).
This is how you do the 50/50 comparison you asked about in your previous post.

[ParkourPenguin]

1. I suppose that depends on what "rand" function you call. If you're talking about the one in the MSVCRT library, then I think that is the case (Google it for more info).

2. call rand pushes the address of the next instruction onto the stack and jumps to wherever the symbol "rand" is located. Assuming "rand" is expecting to get called, it will have a "ret" statement eventually, which will pop that aforementioned address off the stack and jump back to it, presumably with something stored in eax in this case.

or eax,1 performs a bitwise or operation on the eax register and the immediate value 1. Basically, this just makes eax an odd number.

cmp eax,0 compares eax with 0 and sets EFLAGS accordingly. This is next to useless combined with the previous instruction since eax will always be an odd number.

3. ...that is a randomizer. If you want to look at more:
https://en.wikipedia.org/wiki/List_of_random_number_generators
Writing one in assembly isn't any different than writing one in any other language. It just may take more time.

[Dr.Disrespect]

[ParkourPenguin]

I had a momentary lapse of reason when reading that ASM and mistook the bitwise or operator for the bitwise and operator. I apologize for any confusion and have edited my previous post to correct the mistake.

Let's say that call makes eax 6, or 0110 in binary. Then, only focusing on the first nibble, the or instruction would do this:

[Dr.Disrespect]

[ParkourPenguin]

If you're just concerned about powers of 2, then AND it with more bits taken into consideration. Namely, something AND 3 would give a 25% chance of it being 0. Something AND 7 would give a 12.5% chance of it being equal to 0.

If you don't want it to be limited to powers of 2, then you could use DIV to divide EAX by something and test if the remainder is 0. For example, if you want a 1 in 10 chance of something happening:

[Dr.Disrespect]