Hey guys, having a little trouble understanding whether or not a system is causal or not. I d'nt think this classifies as homework; at least I hope not. Basically I'm confused as to how you would go about determining whether or not a system is causal. For example, say any function x[n] = u[n]; So basically the signal is only active for n>=0; y[n] = sin[n]; So you have an output for n<=0 when there is no signal propogating into the system. Thus I would assume that this system is non-causal, because the output is somehow anticipatory. However, what if the output y[n] actually does depend on inputs of 0. So y[n] for n<=0 actually does result from x[n] = 0, wouldn't that make it causal then? Not sure if this makes any sense whatsoever, hopefully someone can share some insight on this topic.