Basic C++ Tutorial

For this first lesson in C++ programming, we will begin with a tutorial on basic input and output. An input device is any device that allows a user to put data into a computer, such as a keyboard or mouse. An output device allows data to be sent out of the computer, usually via a graphical medium, like that of a monitor or printer. In this lesson we will focus on using the keyboard as our input device and the monitor as our output device. In order to achieve access to these devices in C++, we need to include a file in our source code from the standard library, which is packaged with every C++ compiler. We do this by using the include statement.

NOTE: // indicates a comment. Comments are ignored by the compiler.

//Source code View
#include


For header files that are a part of C++'s Standard Library, the filename without the .h extension should be placed within angled brackets as above. If you create your own header file or class, or use any other include file that is not part of the standard library, you must add the file to your working directory and include the extension .h when referencing in your source. When including, you must place the filename between quotation marks. Ex. #include "myClass.h"

We will cover classes in a later tutorial.

Now that we have access to C++'s input and output functions, we want to be able to use them by their standard names, which are in the namespace for the standard library, std.

//Source Code View #include
using namespace std;


We are now ready to use the input and output functions. The two most common are cin and cout.

In order to create our C++ program, we first need a main function. Main is the function that is ran upon program execution. We will have it return an integer, 0 if execution was successful, 1 if there was an error during the program. The program below will run, but it doesn't do anything.


//Source Code View #include
using namespace std;

int main()
{
return 0;
}


NOTE: All statements in C++ are followed by a semicolon.

The first part of the function's signature is its return type, int (integer). We then have the function's name followed by its parameter list in the parentheses. We do not need to pass any arguments to main, so we could have typed void between the parentheses.

Within the body of the function is a return statement. You will notice that all command statements in C++ are followed by a semicolon. We had the function return 0 because at this point in the code the program should end. In fact, our program starts and stops without doing anything but sending a message to the operating system letting it know that everything went OK. If you haven't already ran the program, please compile it and do so.

Now we can display some text in the program using cout, which stands for "console output." In order to achieve this, we type cout followed by the << operator and the string we want as output. In this case, we will be using a string literal.



//Source Code View
#include
using namespace std;

int main()
{
cout << "My First C++ Program" << endl;
return 0;
}


Endl, at the end of the cout statement, signifies a line break. You could also use \n within quotation marks for a line break. See Escape Sequences . It is all a matter of preference at this point whether you use endl or \n. Run the program!

We can now display text on the monitor, but what about getting input from the user? Well, that is also simple when using C++'s cin. Since we are already familiar with the integer data type, we will use an integer to store input from the keyboard. First, we need to create a new variable to hold this data. To do this, type the data type you want to create followed by the variable name you want to use and a semicolon.

//Source Code View
#include
using namespace std;

int main()
{
int age;
cout << "My First C++ Program" << endl;
return 0;
}


We should also change the instructions for the user.

//Source Code View
#include
using namespace std;

int main()
{
int age;
cout << "My Second C++ Program" << endl;
cout << "Please enter your age in years: ";
return 0;
}


We want to be able to get the users age, so we first prompt the user. Then we can use cin to pull in the data. We simply type cin followed by the >> operator and the variable that we want to store data in. You'll notice that the operator used for cin is the opposite of that used for cout. Then, we can print the data back out to the user, using cout. When printing a variable, just use the variable's name without quotes.

//Source Code View
#include
using namespace std;

int main()
{
int age;
cout << "My Second C++ Program" << endl;
cout << "Please enter your age in years followed by : ";
cin >> age;
cout << "\nYou are " << age << " years old." << endl;
return 0;
}

Congratulations, you have now created a C++ program that can get information from a user and display it back to them.

-kolij-