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Introduction to C++ Programs

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Here is a first example of a C++ program, one which virtually every C++ programmer learns when starting off:

// So we can use the "cout" command 
#include <iostream.h>	

void main()
	cout << "Hello World!\n";	/* this is pretty simple */

This program does almost nothing useful except that it gives a new programmer some sense of how a program might be organized. If you compile and run this program, the computer prints out "Hello World!" on your screen, and then halts. Let's look at the parts of this program:

The first line lets the programmer use extra functions, such as cout. You must #include header files (or ".h" files) like these at the start of your program in order to use the functions/variables/classes that they define. The syntax is:

#include <header_file_name>
(Note that some header file names end in .h and others don't).

You can also easily create your own header files for use in your programs if you want to be able to reuse your code or want to better organize your programs.

Above the #include line is a comment. C++ will completely ignore anything you write after two forward slashes (//) until the end of the line. Another way to comment, which you can find a few lines later, is the standard C comment syntax. Simply type any message you want between the start-comment marker (a forward slash followed by and asterisk, /*) and the end-comment marker (the opposite, */). The message can span many lines as needed, as shown in the typical commenting style below:

 * The C++ compiler can not see ANYthing I type here 
 * because I typed the symbol /* However, it can see my
 * code again after I type the next line.

The third line of the program is blank, which is perfectly legal. You can insert as many extra blank lines or "white space" as you'd like in order to make your program more (or less) readable. Spaces and tabs are also considered white space.

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