Why to use default constructor?whats the use of default constructor?

Question

class sample
{
int a;
public:sample()
{
a=0;
}
};

Answer 1

For Initialize variable

Answer 2

default constructor is the non-parameterised construction that is used to assign default values to member variables . it is good practice to use default constructor because if u don't use ur own default constructor then all the class variable will contain garbage values and if used before initialisation they may give unexpected results.

Answer 3

They are good practice for a scenario for when someone else intends to use or build upon your code in a way that you might not be able to account for.