Ashish Kumar

"Main" is a particular global function in C/C++ from where the program/exe is supposed to start.
In your question "void" means the return type, which means not returning anything. But void as a return type for main is considered as the WRONG usage (although some compilers allow it.).
The return type of main should be INT. For normal termination, you may return 0 from the main function. (That's also the default value of the return from main.). For abnormal termination of your program, the return value will be non zero.
If you are using UNIX environment, you can check the return value of your last command (example your program) by typing echo $? on prompt.
But before this - you will have to understand many things, I hope you do. Like Global function, return type, keyword, data type, compiler. So many terms used in this discussion. I assume it's time for you to dive in.

1) Use Recursion. (as given in the other answer). But in Recursion there is one drawback, if the number is enormous, your process stack may overflow, and your program may terminate.
2) The other way (trick) is to
- Design a class.
- In the constructor of the class (which should not take any argument), in the constructor body, print the line "I love programming".
After that, in your primary function, declare an array or vector of this class object of size equal to what the user has entered.
Don't forget to check the negative or zero aspect of the input number. It should be a positive integer.

Writing big programs in C++ is as safe as in any other language.  
By safe, I think you mean error-free, crash-free etc.  (Behaviour of a program).
Language has nothing to do with the safety aspect. You may end up making blunders in any language.
Nowadays, big programs (means very very large) are being written in many languages.

Never, it's the programming skills that matter, irrespective of the language can be anyone. In general, you should be familiar with one compiler-based and one interpreted language. (But it's not mandatory). In your career, you may come across situations, where you will have to quickly learn a new language and solve the problems in the new language. 
If you have learned one language,  I am sure you will learn all other too very easily.

It's essential if you work in products/areas based on C/C++.
If you are a student, anyone language is sufficient, be it C/C++ or Java. If it's object-oriented like C++ or java, it is better.
Otherwise, you will be judged by your programming skills (be it any language.). Be confident that if you can write code in one language, then you will be able to write code in any other language too. It's just a matter of time.

Programming skills are more important than the language part.