First day of C++ programming [College]

//My first day of C++ Programming...

// pgm1.cpp - My C++ program
#include<iostream> //include in/output of the actual program
using namespace std; //include namespace so you don't have to keep using std:: before the functions in the class

int _age; //global variable that can be used throughout the scope of the program

int main() //scope of program
{
    /*
    int x = 0;
    char y;
    float z;
    long a;
    double b; //these are variables

    std::cout<< "int x = " << sizeof(x) << std::endl;
    std::cout<< "char y = " << sizeof(y) << std::endl;
    std::cout<< "float z = " << sizeof(z) << std::endl;
    std::cout<< "long a = " << sizeof(a) << std::endl;
    std::cout<< "double  b = " << sizeof(b) << std::endl;
    //std can be removed as it's added throughout the scope of the entire program
    std::cin.get();

    cout<<"hello, how old are you?: ";
    cin >> _age; //age is entered here
    cout<< "You are: "<<_age <<" years old";

    cin.get();
    cin.get();
    */

    cout<<"Enter your age: "; //cout = text outputted to console
    cin >> _age;
    int date = 2014; //int is allocated to 4 bytes in memory in RAM
    int outcome;
    outcome = date - _age;
    cout<<"You were born in the year: " << outcome;
    cin.get(); //Waits for user input
    cin.get();

    return 0;
}
//I already knew a lot of the stuff already, but thought I would share. :D
//BaSs_HaXoR