using namespace std;"in the code can we compile the codes

[sana.pari]

with out using "using namespace std;"in the code can we compile the codes are taught in previous lectures? in your prefered Dev-C++ 4.9.9.2?

if This thing is mentioned in any previous lecture please let me know.

[Support]

Dear student!
There are two ways to do this thing.
Method 1:
#include<iostream>
using namespace std;

Method 2: #include<iostream.h>