Introduction to C++

C++ is a programming language which allow you to control your computer, making it do what you want it to do. This programming tutorial series is all about helping you to take full advantage of C++.

C++ Compilers

The very first thing you need to do, before starting out in C++, is to make sure that you have a compiler. What is a compiler, you ask? A compiler turns the program that you write into a executable that your computer can actually understand and run. If you’re taking a course, you probably have one provided through your school. If you’re starting out on your own, your best bet is to use Code::Blocks. Our page on setting up Code::Blocks will take you through setting up the Code::Blocks compiler in great detail.

Introduction to the C++

A C++ program is a collection of commands, which tell the computer to do “something”. This collection of commands is usually called C++ source code, source code or just code. Commands are either “functions” or “keywords”. Keywords are a basic building block of the language, while functions are, in fact, usually written in terms of simpler functions–you’ll see this in our very first program, below. (Confused? Think of it a bit like an outline for a book; the outline might show every chapter in the book; each chapter might have its own outline, composed of sections. Each section might have its own outline, or it might have all of the details written up.) Thankfully, C++ provides a great many common functions and keywords that you can use.

But how does a program actually start? Every program in C++ has one function, always named main, that is always called when your program first executes. From main, you can also call other functions whether they are written by us or, as mentioned earlier, provided by the compiler.

So how do you get access to those prewritten functions? To access those standard functions that comes with the compiler, you include a header with the #include directive. What this does is effectively take everything in the header and paste it into your program.

Let’s look at a working program:

#include <iostream>

using namespace std;

int main()
{

cout<<“Hello World!\n”;
cin.get();

}

The #include is a “preprocessor” directive that tells the compiler to put code from the header called iostream into our program before actually creating the executable. By including header files, you gain access to many different functions.

The next important line is int main(). This line tells the compiler that there is a function named main, and that the function returns an integer, hence int. The “curly braces” ({ and }) signal the beginning and end of functions and other code blocks. You can think of them as meaning BEGIN and END.

In C++, however, the cout object is used to display text (pronounced “C out”). It uses the << symbols, known as “insertion operators”, to indicate what to output. cout<< results in a function call with the ensuing text as an argument to the function. The quotes tell the compiler that you want to output the literal string as-is. The ‘\n’ sequence is actually treated as a single character that stands for a new line.

The next command is cin.get(). This is another function call: it reads in input and expects the user to hit the return key. Many compiler environments will open a new console window, run the program, and then close the window. This command keeps that window from closing.

Upon reaching the end of main, the closing brace, our program will return the value of 0 (and integer, hence why we told main to return an int) to the operating system. This return value is important as it can be used to tell the OS whether our program succeeded or not. A return value of 0 means success and is returned automatically (but only for main, other functions require you to manually return a value), but if we wanted to return something else, such as 1, we would have to do it with a return statement:

#include <iostream>

using namespace std;

int main()
{

cout<<“Hello World!\n”;
cin.get();

return 1;

}

C++ Comments

When you tell the compiler a section of text is a comment, it will ignore it when running the code, allowing you to use any text you want to describe the real code. To create a comment use either //, which tells the compiler that the rest of the line is a comment, or /* and then */ to block off everything between as a comment. Certain compiler environments will change the color of a commented area, but some will not. Be certain not to accidentally comment out code (that is, to tell the compiler part of your code is a comment) you need for the program. When you are learning to program, it is useful to be able to comment out sections of code in order to see how the output is affected.

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