If I create a vector<int> of 100 elements and a vector<char> of 100 elements, will there be any difference in the total memory used by them?

Yes, if sizeof(int)>sizeof(char) on your platform, then vector<int> consumes more memory than vector<char>, because the Standard requires that "the elements of a vector are stored contiguously, meaning that if v is a vector where T is some type other than bool, then it obeys the identity &v[n] == &v[0] + n for all 0 <= n < v.size()."

or which is more efficient?

What do you mean by saying "more efficient"? vector<char> consumes less memory, but accessing its elements might be less efficient on some platforms.

On 8/21/13 7:33 AM, Lloyd wrote:

Hi,

If I create a vector<int> of 100 elements and a vector<char> of 100 elements, will there be any difference in the total memory used by them? or which is more efficient?

Thanks, Lloyd

Since on most machines, an int is bigger than a char, the vector<int> will allocate more memory than a vector<char>. Note that the memory for the elements will NOT show up in the sizeof() the vector, as the vector object itself doesn't hold the elements, but just a control block, the elements are normally stored on the heap. As to efficiency, if you are only storing chars, than the vector<char> is probably more efficient, if you are actually storing something bigger (like an int), than a vector<char> is probably the wrong thing to be using in the first place. -- Richard Damon