Reading from a Stream

Having asked the user for input, we next want to read that input. We start by defining two variables named v1 and v2 to hold the input:

int v1 = 0, v2 = 0;

We define these variables as type int, which is a built-in type representing integers. We also initialize them to 0. When we initialize a variable, we give it the indicated value at the same time as the variable is created.

The next statement

std::cin >> v1 >> v2;

reads the input. The input operator (the » operator) behaves analogously to the output operator. It takes an istream as its left-hand operand and an object as its right-hand operand. It reads data from the given istream and stores what was read in the given object. Like the output operator, the input operator returns its left-hand operand as its result. Hence, this expression is equivalent to

(std::cin >> v1) >> v2;

Because the operator returns its left-hand operand, we can combine a sequence of input requests into a single statement. Our input operation reads two values from std::cin, storing the first in v1 and the second in v2. In other words, our input operation executes as

std::cin >> v1;
std::cin >> v2;