Meaning of using namespace std;

Answer 1

Check this

https://medium.com/breaktheloop/why-using-namespace-std-is-used-after-including-iostream-dc5ae45db652

Answer 2

e_o Kindly use the Search bar .Check this :
https://www.sololearn.com/learn/CPlusPlus/4120/
https://www.sololearn.com/Discuss/2549418/?ref=app