c++ - What is the difference between &vector[0] and vector.begin()?

Question

This question is related with item 16 of effective stl book which states that while using vector(lets assume vector<int>vec) instead of array in a legacy code we must use &vec[0] instead of vec.begin() :

 void doSomething(const int* pInts, size_t numlnts);  
 dosomething(&vec[0],vec.size()); \correct!! 
 dosomething(vec.begin(),vec.size()); \ wrong!! why??? 

The book states that vec.begin() is not same as &vec[0] . Why ? What the difference between the two ?

Answer 1

Formally, one produces an iterator, and the other a pointer, but I think the major difference is that vec[0] will do bad stuff if the vector is empty, while vec.begin() will not.