reverse (left) arrow in an algorithm?
There is a algorithm, in which author has written steps of algorithm like this,
1.initialization:set up the threshold (th) and maximum iteration number, $I$.
$i\leftarrow 0$
2.calculate x
while (x>th) do
$i\leftarrow i+1$
...
end while
what does this left arrow means here?
It means "set", or assignment. So in most syntax, those lines are i = 0 and i = i + 1. This was probably avoided because in math, $=$ means ==, and assignment isn't a useful concept.