Displaying an 8-bit vector with 8 LEDs (Demultiplexer)

Hello there,
I have an important project to do here. All is working fine, I have only one problem, in its final part. I have to display with 8 LEDs a 8-bit Vector, I took a Demultiplexer, with the 3 selection lines, which are attached to 3 digital PINs of Arduino, but it doesn't work! All the LEDs turn on randomly, I've tried everything, but still nothing.
All I have to do is this. Can you guys help me?
Thanks!

Same school project as before?

Well, start by explaining whatever you mean by "display ... a 8-bit Vector"?

Now show us your circuit diagram or a perfectly focussed, daylight photograph showing all details of your current assembly and in "code" tags according to the instructions, your code.


By the way, your teacher, if he is setting you examples with an Arduino - would be watching this forum, wouldn't he?

Well, start by explaining whatever you mean by "display ... a 8-bit Vector"?

I always told my students that a vector was a force coupled with a direction. Rather like f**k off.

I apologize, I can't go on with this thread, because of my english level, i wouldn't be able to describe everything I need to make you understand perfectly the main project... I'm so sorry...... I move to the italian section though!
However, thanks to all.
Bye!