Thread: reason for _funname() and funname()

Hi I have seen this before but I am confused as to why people do so. If there is a technical term to better define it please do let me know

If you look at the code below

Code:

Code:

class _Correl
{
public:
    double Nom;
    double DeNom1, DeNom2;

    _Correl( double val ) { Nom = DeNom1 = DeNom2 = val; }
    void operator=( double val ) { Nom = DeNom1 = DeNom2 = val; }
    operator double() { return Nom / sqrt( DeNom1 * DeNom2 ); }
};

class Correl
{
public:
    typedef _Correl result_type;

    Correl() { mean1 = mean2 = 0; }
    Correl( double _mean1, double _mean2 = 0 ) { mean1 = _mean1; mean2 = _mean2; }

    template<class Val> result_type operator () ( result_type s, Val val1, Val val2 )
        {
            double v1 = val1 - mean1;
            double v2 = val2 - mean2;
            s.Nom += v1 * v2;
            s.DeNom1 += v1 * v1;
            s.DeNom2 += v2 * v2;
            return s;
        }
protected:
    double mean1;
    double mean2;
};

there are terms like "class Correl" and "typdef _Correl"

"mean1 = _mean1" "double _mean1"

Now I do understand that mean1 and _mean1 are different
but why do codders (at higher level) use "_name of (variable/function etc.).

I have seen this in header files of VC++ as well?

If there is some documentation that I could refer on this matter I would like to know.

Thanks
Nipun