# C++

## Compiling and Executing a program

Once we created a program we need to compile it. How your compile a program depends on your operating system and compiler. If we are using a command-line interface in a unix system we can compile it as follow:

$g++ -o sum sum.cpp  Where -o is an argument to te compiler and names the file in which to put executable file. This command generates an executable file named sum, to execute in the current directory: $ ./sum


Let’s consider the following example:

#include <iostream>

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


iostream is a standard library that provides IO objects. To handle an input, we use an object cin (istream), for output we use an cout (ostream).

1. The first line tells the compiler that we want to use iostream library.
2. The first statement in the body of main executes an expression.
std::cout << "Enter two numbers" << std::endl;

1. The << operator takes two operands: The left-hand operand must be an ostream object, the right operand is a value to print.
2. The endl is a special value called manipulator. Writting endl has the effect of ending the current line and flusing the buffer associated with that device.
3. The prefix std:: indicates that the names cout and endl are defined inside the namespace named std. The namespaces allow us to avoid inadvertent collisions between the names.
4. The statement std::cin >> v1 >> v2; define 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.

## HelloWorld

So this is the Hello world example in C++

#include <iostream>

int main()
{
std::cout << "Hello World!" << std::endl;
return 0;
}