Program to add two numbers in C++

By: Stanley B. in C++ Tutorials on 2011-02-19

Using the IO library, we can extend our main program to ask the user to give us two numbers and then print their sum:

#include <iostream>
int main()
{
std::cout << "Enter two numbers:" << std::endl;
int v1, v2;
std::cin >> v1 >> v2;
std::cout << "The sum of " << v1 << " and " << v2
<< " is " << v1 + v2 << std::endl;
return 0;
}

This program starts by printing

Enter two numbers:

on the user's screen and then waits for input from the user. If the user enters

3 7

followed by a newline, then the program produces the following output:

The sum of 3 and 7 is 10

The first line of our program is a preprocessor directive:

#include <iostream>

which tells the compiler that we want to use the iostream library. The name inside angle brackets is a header. Every program that uses a library facility must include its associated header. The #include directive must be written on a single line the name of the header and the #include must appear on the same line. In general, #include directives should appear outside any function. Typically, all the #include directives for a program appear at the beginning of the file.

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