Hello and welcome back.
In this lesson, we are going to take a look at the sign flag, -.
This flag indicates the sign of the result of an arithmetic or logical operation.
It is set if the result is negative or cleared if the result is positive.
So let's take a look at x64dbg to see how it works.
The sign flag register is over here, -, as you can see.
So now I've opened the template two
in the x64dbg. I have a breakpoint set, and I will now run to my breakpoint.
Then I will step over until I reach to a blank line.
Now I'm going to perform an arithmetic operation on -.
I'm going to add ten to -.
So let's do that.
Now add -, ten.
Click okay.
Currently, - has got the value one,
and I'm going to add ten to it.
And the result should be a positive number.
And take a look at the sign flag. Sign flag is currently cleared.
So let's step over.
And the result is here,
and the sign flag is cleared,
still cleared.
That means the result is a positive number.
Now let's try to do an arithmetic operation, subtraction this time, to get the result which is a negative
number.
And we will try that on -.
- is now one, and I'm going to minus ten from -.
So go to a new line.
Type sub -, ten.
Okay, now -, one. I'm going to minus ten from one.
So the result should be a negative number.
And watch the - flag. Step over. The - flag is set. It is one.
Therefore, the result is a negative number, as you can see.
So this is how the flag is used in the assembly programming in x64dbg.
That's all for this video.
Thank you for watching.