C++ Notes

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  • Topic: Statement, Switch statement, Control flow
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Getting Set Up - 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 an 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 with MinGW. If you're on Linux, you can use g++, and if you're on Mac OS X, you can use XCode. (If you are stuck using an older compiler, such as Turbo C++, you'll need to read this page on compatibility issues.) If you haven't yet done so, go ahead and get a compiler set up--you'll need it for the rest of the tutorial. Intro to the C++ Language

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 canuse.

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: 123456789| #include <iostream>   using namespace std;   int main() {   cout<<"HEY, you, I'm alive! Oh, and Hello World!\n";   cin.get(); }| Let's look at the elements of the program. 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. For example, the cout function requires iostream. Following the include is the statement, "using namespace std;". This line tells the compiler to use a group of functions that are part of the standard library (std). By including this line at the top of a file, you allow the program to use functions such as cout. The semicolon is part of the syntax of C++. It tells the compiler that you're at the end of a command. You will see later that the semicolon is used to end most commands in C++.

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 andEND.

The next line of the program may seem strange. If you have programmed in another language, you might expect that print would be the function used to display text. 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 newline (we'll talk about this later in more detail). It...
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