well remember when you have an array of 100 items, the last item is in the 99th spot so on that subject:

Code:
#define NUMPACKETS 100
double arrivalTimeArray[NUMPACKETS];
for(int i=0; i<NUMPACKETS; i++) { // its not <= because it doesnt go up to 100
			next = expDistArrival();
			arrivalTimeArray[i] = next + current;
			current = arrivalTimeArray[i];
	}
	// double test =  arrivalTimeArray[100]; there is no 100th spot