C++ How to Program, 10/e

... using namespace std;

which enables a program to use all the names in any standard C++ header (such as <iostream>) that a program might include. From this point forward in the book, we’ll use the preceding directive in our programs.2

2. In Chapter 23, Other Topics, we’ll discuss some issues with using directives in large-scale systems.

Variable Declarations and Reading the Inputs from the User

Lines 12–13

int number1{0}; // first integer to compare (initialized to 0)
int number2{0}; // second integer to compare (initialized to 0)

declare the variables used in the program and initialize them to 0.

Line 16

cin >> number1 >> number2; // read two integers from user

uses cascaded stream extraction operations to input two integers. Recall that we’re ...