How many languages you should learn to be a successful programmer?

Question

At sololearn platform 12 languages are available. I think there are three types of programmers.
1. Desktop Application Programming
(C#, SQL, etc)
2. Website Application Programming
(PHP, HTML , MySQL etc.)
3. Mobile Application Programming
(Java, XML etc )
why we needed python, ruby etc?
Can one person grasp all these languages at professional level?
which language we should adopt C++ or C#, PHP or Ruby , HTML or XML ?

Answer 1

Being a successful programer is about handling any problem that you encounter be its c++,java,python,ruby or whatever. Not to mention your skills have to be updated with latest technologies or you will be stuck with outdated stuff.

Answer 2

It depends on what you want to program. I'm interested in web programming ( php, java, javascript, python, html, css, sql). If you want to be app programer ( C, C++, java, javascript, sql, qbasic, python, logo..etc)

Answer 3

I have already study Java and C#. Now I think I'll learn Clipper.

Answer 4

i need to this program