Welcome to About.com's C++ tutorial. The lessons in this
tutorial will take you from being a beginner to being able to
write real programs in C++.
C++ is a compiled language. The C++ compiler
is a program that reads source
code, which is the C++ code written by a programmer, and
it produces an executable or binary file that in a format that
can be read and executed (run) by a computer. The source file
is a plain text file containing your code. The executable file
consists of machine code, 1's and 0's that are not meant to be
understood or read by people, but only by computers.
The best way to learn anything is to jump right in, so
let's start by writing a simple C++ hello world program.
First Program
#include <iostream>
using namespace std;
int
main()
{
cout
<< "Hello World From
About\n";
}
|
Line 1: #include
<iostream>
As part of
compilation, the C++ compiler runs a program called the C++ preprocessor.
The preprocessor is able to add and remove code from your
source file. In this case, the directive #include
tells the preprocessor to include code from the file iostream.
This file contains declarations
for functions
that the program needs to use, as well as available classes.
Line 2: using namespace
std
C++ supports the concept
of name spaces. Essentially, this allows variables
to localized to certain regions of code. The command using
namespace std allows all objects
and functions from the standard input and output library to be
used within this program without explicit qualifications.
Namespaces are an advanced concept. For now, all you need to
know is that this line allows simple use of the standard
library.
Line 3: int
main()
This statement
declares the main function. A C++ program can contain many
functions but must always have one main function. A function
is a self-contained module of code that can accomplish some
task. Functions are examined in a later tutorial. The "int"
specifies the return type of main to be an integer. An
explicit value may be returned using a return statement. In
this case, 0 is returned be default.
Line 4: {
This
opening bracket denotes the start of the program.
Line 5: cout << "Hello From About\n";
cout is a object from a
standard C++ library that has a method used to print strings
to the standard output, normally your screen. The compiler
links code from these standard libraries to the code you have
written to produce the final executable. The "\n" is a special
format modifier that tells the method to put a line feed at
the end of the line. If there were another "cout" in this
program, its string would print on the next line.
Line 6: }
This
closing bracket denotes the end of the program.
That's it. To get the most of this series of tutorials, you
should get access to both a text editor and a C++ compiler.
Some instructions for doing this are in our tutorials on
compiling.
John
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