1. Headers should not include using declaration
Code inside headers ordinarily should not include using declarations. The reason is that the contents of a header are copied into the including program‘s text. If a header has a using declaration, then every program that includes that header gets the same using declaration. As a result, a program that does not intend to use the specified library name might encounter unexpected name conflicts.
2. Deal with characters in string( with functions in <cctype> header)
isalnum(c): true if c is a letter or digit
isalpha(c): true if c is a letter
isdigit(c): true if c is a digit
islower(c): true if c is a lowercase letter
isspace(c): true if c is a whitesapce
isupper(c): true if c is an uppercase letter
tolower(c): return lowercase letter
toupper(c): return uppercase letter
3. Different between pointer and iterator
Pointer is a built-in type whereas iterator is a class. Pointer is avaiable for all type of objects whereas iterator is only available for containers.
4. Vector and array
Similarity: they all store a collection of variables of a single type and we can access their element by position.
Difference: elements in array is stored in continuous space whereas elements in vector can be stored in non-continuous space. Array is fixed size and we can‘t add or remove element from a array. On the contrary, the size of a vector can be changed by adding or removing elements from it.
4. There is no arrays of references
Namespace, string, vector and array
原文：http://www.cnblogs.com/Kai-Xing/p/4005075.html