Problem with octave 3.8.0

[laura novoa]

I am using Octave 3.8.0, I got it in
:https://sourceforge.net/projects/octave/files/Octave%20MacOSX%20Binary/2013-12-30%20binary%20installer%20of%20Octave%203.8.0%20for%20OSX%2010.9.1%20%28beta%29/

I have been using it for a few days without any problem, but I tried to solve
a simple matrix equation (A*x=v) and in order to do that I had to write the
following character:    \  (I wanted to write: A\v)  
Octave wouldn't let me introduce this character nor these two:   [ ]
In contrary I can write characters like: ^, * or ( ). 
I really don't understand it.