iostream.h 与 iostream

http://www.devx.com/tips/Tip/14447

写法一：
#include <iostream.h>
写法二：
#include <iostream>
using namespace std;

上面两种方式，都可以在VC6.0编译通过，但是两者具体有什么区别？还是没有区别，只是写法不一样而以，我查了很久，有很多描述，但是还是没有一个清晰的概念。

下面这段文字是我觉得描述的比较清楚的：

<iostream.h> or <iostream>?

Although the <iostream.h> library was deprecated for several years, many C++ users still use it in new code instead of using the newer, standard compliant <iostream> library. What are the differences between the two? First, the .h notation of standard header files was deprecated more than 5 years ago. Using deprecated features in new code is never a good idea. In terms of functionality, <iostream> contains a set of templatized I/O classes which support both narrow and wide characters. By contrast, <iostream.h> classes are confined to char exclusively. Third, the C++ standard specification of iostream’s interface was changed in many subtle aspects. Consequently, the interfaces and implementation of <iostream> differ from <iostream.h>. Finally, <iostream> components are declared in namespace std whereas <iostream.h> components are declared in the global scope. Because of these substantial differences, you cannot mix the two libraries in one program. As a rule, use <iostream> in new code and stick to <iostream.h> in legacy code that is incompatible with the new <iostream> library.