Calling functions from main() in c++

I came across a program with 开发者_如何转开发10 header and 10 source files. I read in my text book that the functions are called from main. But how can I pass data to so many functions from main()?

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Functions don't necessarily need to called from main. They can be called by other functions. For example:

int foo(int x)
{
    return x*x;
}

int bar(int x)
{
   return foo(x) + 1;
}

int main()
{
    int a = bar(42);
    std::cout << a << std::endl;
    return 0;
}

Note that foo() is never called directly from main().

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To my mind, this phrase isn't correct, but I guess what was meant to be said could be rephrased like "Every function or class method that you implement and use would be somehow called from your main() routine"

And somehow in this context would actually mean directly or indirectly - via other functions / function wrappers.

Anyway, the idea should be clear - any significant action that is done in your application is actually done using some function call from your main() routine, which is sometimes also called application root (try to think of your application as a tree of function calls and then your main() function would be right in the top of your tree).