iostream

By including C++‘s standard input/output library <iostream>, we can create both inputs with cin and outputs with cout through the command line.

Command Line Interface: The command line is a text interface for your computer. It’s a program that takes in commands, which it passes on to the computer’s operating system to run.

Import the Library

To start, let’s include the iostream library at the top of our file:

#include <iostream>

NOTE: When you include libraries you do not need semicolons!

Now let’s get into the actual input and output.

Syntax

We use std:: to say in simple terms “Inside the standard library we are using…”. In this specific case, we are using std::cin (console input from the standard library), std::cout (console output from the standard library), and std::string (a non-fundamental type). For any class, type, etc. that is not included in the C++ language, we access it using libraries or headers. To specify which library we are extracting them from we use the “::” syntax.

NOTE: The use of std can be avoided by writing the following line of code underneath the library imports:

using namespace std;

With this line, we no longer have to include std:: when referencing something from the standard library.

Basic Output

To start a line of output, we use cout or “console out”.

To end an output line you would finish with either endl or '\n'.

\n counts as a single character despite containing 2 characters at first glance. You can think of the backslash as a command. This is faster than writing endl not only for the user but also for the computer when executing the program.

cout << "hello, world\n";
//  OR
cout << "hello, world" << endl;

These 2 variations work interchangeably. I prefer the \n.

Multi-threaded output

To include multiple pieces or variable types in an output you use the insertion operators << like glue. For example:

cout << "this is an example of how to print the number " << 1 << '\n';

You should see the result of this is an example of how to print the number 1 where the integer 1 could be replaced by any type of variable.

Notice how I left a space after the number to allow for space in front of the integer/variable. This is purely preference. I believe it allows for a more desirable outcome.

Basic Input

To get input, we use cin or “console in”.

int input;
cin >> input;

Where input will hold the data we would like to extract.

NOTE: The “extraction operators” >> are similar to the insertion operators except they are flipped. This allows us to extract the user’s input from the console.

Wrapping Up

To put it all together, let’s look at a simple program:

cout << "enter your age: ";
int age;
cin >> age;
cout << "you are " << age << " years old!\n";

We have accomplished the following:

1. Prompted the user to input data.
2. Extract the data from the command line.
3. Output the data that we extracted.