Consider the following class:

 class A{public: A(int size);private: int size;};

You can initialize the member size in at least three forms:

 A::A (int size) : size (size) { } // 1A::A (int size) { this->size = size; } // 2A::A (int size) { A::size = size; } // 3

All of these forms are legal and portable. However, the first one is preferable because the use of a member initialization explicitly indicates that you’re actually initializing a data member rather than assigning a value to it. Note that if the member being initialized is an object, this form is also more efficient than the rest.As for using identical names for the data member and the argument, the compiler is clever enough to distinguish between the two correctly. However, to avoid confusing a human reader, you might consider different names, e.g.:

 A::A (int sz) : size (sz) { }